ROS in pro-inflammatory mediators-induced airway and pulmonary diseases

Biochemical Pharmacology 84 (2012) 581–590

Contents lists available at SciVerse ScienceDirect

Biochemical Pharmacology journal homepage: www.elsevier.com/locate/biochempharm

Commentary

Role of NADPH oxidase/ROS in pro-inflammatory mediators-induced airway and pulmonary diseases I-Ta Lee a, Chuen-Mao Yang b,* a b

Department of Anesthetics, Chang Gung Memorial Hospital and College of Medicine, Chang Gung University, Kwei-San, Tao-Yuan, Taiwan Department of Physiology and Pharmacology and Health Aging Research Center, College of Medicine, Chang Gung University, Kwei-San, Tao-Yuan, Taiwan

A R T I C L E I N F O

A B S T R A C T

Article history: Received 14 March 2012 Accepted 2 May 2012 Available online 12 May 2012

Reactive oxygen species (ROS) are products of normal cellular metabolism and are known to act as second messengers. Under physiological conditions, ROS participate in maintenance of cellular ‘redox homeostasis’ in order to protect cells against oxidative stress. In addition, regulation of redox state is important for cell activation, viability, proliferation, and organ function. However, overproduction of ROS, most frequently due to excessive stimulation of either reduced nicotinamide adenine dinucleotide phosphate (NADPH) by pro-inflammatory cytokines, such as tumor necrosis factor-a (TNF-a) and interleukin-1b (IL-1b) or the mitochondrial electron transport chain and xanthine oxidase, results in oxidative stress. Oxidative stress is a deleterious process that leads to airway and lung damage and consequently to several respiratory inflammatory diseases/injuries, including acute respiratory distress syndrome (ARDS), asthma, cystic fibrosis (CF), and chronic obstructive pulmonary disease (COPD). Many of the known inflammatory target proteins, such as matrix metalloproteinase-9 (MMP-9), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), cyclooxygenase-2 (COX-2), and cytosolic phospholipase A2 (cPLA2), are associated with NADPH oxidase activation and ROS overproduction in response to pro-inflammatory mediators. Thus, oxidative stress regulates both key inflammatory signal transduction pathways and target proteins involved in airway and lung inflammation. In this review, we discuss mechanisms of NADPH oxidase/ROS in the expression of inflammatory target proteins involved in airway and lung diseases. Knowledge of the mechanisms of ROS regulation could lead to the pharmacological manipulation of antioxidants in airway and lung inflammation and injury. ß 2012 Elsevier Inc. All rights reserved.

Keywords: Antioxidants Inflammation NADPH oxidase Reactive oxygen species Respiratory inflammatory diseases Signaling pathways

1. Introduction Inflammation is a protective response to cellular and tissue damage/injury. The purpose of this process is to destroy and remove the injurious agents and injured tissues, thereby promoting tissue repair. When this beneficial response occurs in an uncontrolled manner, the result is excessive cellular/tissue damage that results in chronic inflammation and destruction of normal tissue [1]. Moreover, inflammatory airway and lung diseases are characterized by chronic inflammation and oxidant/ antioxidant imbalance, a major cause of cell damage/injury. Reactive oxygen species (ROS) are widely recognized as important mediators of cell growth, adhesion, differentiation, senescence, and apoptosis [2]. Excessive production of ROS (termed ‘‘oxidative

* Corresponding author at: Department of Physiology and Pharmacology, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-San, Tao-Yuan, Taiwan. Tel.: +886 032118800x5123; fax: +886 032118365. E-mail address: [email protected] (C.-M. Yang). 0006-2952/$ – see front matter ß 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.bcp.2012.05.005

stress’’) by NADPH oxidase (NOX) is commonly thought to be responsible for tissue injury associated with a range of respiratory inflammatory diseases/injuries, such as acute respiratory distress syndrome (ARDS), asthma, cystic fibrosis (CF), and chronic obstructive pulmonary disease (COPD) [1]. On the other hand, many of the known inflammatory target proteins, such as matrix metalloproteinase-9 (MMP-9), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), cyclooxygenase-2 (COX-2), and cytosolic phospholipase A2 (cPLA2), are associated with NOX activation and ROS overproduction induced by pro-inflammatory mediators, such as tumor necrosis factor-a (TNF-a) and interleukin-1b (IL-1b) [3–7]. Lung cells, in particular alveolar epithelial type II cells, are susceptible to the injurious effects of oxidants. It has been shown that lung cells release inflammatory mediators and cytokines/chemokines, such as IL-1b, IL-6, IL-8, and TNF-a in response to oxidative stress [1]. In addition, ROS can initiate inflammatory responses in the airways and lungs through the activation of redox-sensitive transcription factors, including activator protein-1 (AP-1), hypoxia-inducible factor (HIF)-1, and nuclear factor-kappaB (NF-kB) [8]. Thus, this review

582

I.-T. Lee, C.-M. Yang / Biochemical Pharmacology 84 (2012) 581–590

will focus on some general aspects of NOX/ROS regulation and summarize current knowledge regarding the presence and functional roles of NOX/ROS within the respiratory system, and their proposed involvement in the expression inflammatory target proteins in response to proinflammatory mediators during airway and lung inflammation. The pharmacological interventions protect against oxidative stress-induced airway and lung diseases will be discussed. 2. NADPH oxidase is a major source of ROS With the exception of unusual circumstances, such as exposure to UV light, ionizing radiation, and other high energy sources, ROS are generally generated in cells by electron transfer reactions, which can be enzymatic or non-enzymatic [1]. Epithelial cells, resident macrophages, endothelial cells, and recruited inflammatory cells, such as neutrophils, eosinophils, monocytes, and lymphocytes, produce ROS in response to increased levels of secretagogue stimuli [9]. Moreover, activation of macrophages, neutrophils, and eosinophils results first in the formation of superoxide anion, which is converted to hydrogen peroxide by superoxide dismutase (SOD), and hydroxyl radicals is formed nonenzymatically in the presence of Fe2+ as a secondary reaction [1,9]. ROS generated by phagocytes at sites of inflammation are a major cause of cell and tissue damage/injury associated with various chronic inflammatory airway and lung diseases. ROS are intracellularly generated from several sources, including mitochondrial respiration, cytochrome P450, the NOX system, xanthine/xanthine oxidase, and metabolism of arachidonic acid [9]. However, the major ROS generating enzyme is NOX, a membranebound multi-component enzyme complex that is present in phagocytes as well as non-phagocytic cells [4]. ROS produced by

NOX have two major roles. First, superoxide produced by NOX2 is required for respiratory burst that occurs in phagocytes, leading to microbial killing. The second role of NOX is associated with the regulation of cell signaling [10]. ROS derived from NOX can specifically and reversibly react with proteins, altering their activity, localization, and half-life [10]. The members of the NOX family exist in various supergroups of eukaryotes but not in prokaryotes, and play crucial roles in a variety of biological processes, such as host defense, signal transduction, and hormone synthesis. Activated phagocytic cells generate ROS via assembly and activation of the NOX complex, which comprises membraneassociated flavocytochrome b558 (gp91phox) and p22phox and various cytosolic co-factors (p47phox, p67phox, and p40phox, and the GTPase, Rac1), and mediates transmembrane electron transfer from the major cellular electron donor, NADPH, to reduce molecular O2 to superoxide anion (O2 ) and hydrogen peroxide (H2O2) [11]. A number of homologs of the main business end of NOX, gp91phox, have been discovered, and mammalian systems are now known to contain seven NOX homologs, comprising NOX1-5 (NOX2 being the new name for gp91phox) and two larger Dual Oxidases, DUOX1 and DUOX2, which are widely expressed in many cell types to mediate a variety of biological functions, such as cell mitosis, differentiation, migration, and immune regulation [11] (Fig. 1). Similar to NOX2, activation of NOX1 and NOX3 also requires association with p22phox, and assembly with Rac 1 and cytosolic co-factors (p47phox and p67phox or their homologs, NOX organizer 1 (NOXO1) and NOX activator 1 (NOXA1). NOX4 also requires p22phox, but appears to be constitutively active without the need for activation of other co-factors [11]. NOX5 and DUOX1/2 differ from the other NOX homologs and contain additional intracellular Ca2+-binding EF-hand domain regions, and are primarily regulated by Ca2+ signaling, without the need for

Fig. 1. NOX enzymes in lung cellular physiology. NOX/DUOX isoforms are expressed in a number of lung cell types, including airway/alveolar epithelial, endothelial, and mesenchymal cells, extending from the proximal trachea and large airways to terminal bronchioles and alveoli. Proposed functions of NOX isoforms are indicated in various cell types.

I.-T. Lee, C.-M. Yang / Biochemical Pharmacology 84 (2012) 581–590

association with p22phox or other cytosolic co-factors [12]. The two DUOX proteins contain an additional extracellular peroxidase homology domain, with functional peroxidase activity in lower organisms but as yet unclear function in mammalian homologs [12]. 3. Oxidative stress and pro-inflammatory genes Inflammatory mediators play a key role in chronic inflammatory processes and appear to determine the nature of the inflammatory responses by directing the selective recruitment and activation of inflammatory cells and their perpetuation within the airways and lungs. In in vitro studies, using macrophages, alveolar and bronchial epithelial cells, ROS have been shown to induce gene expression of inflammatory mediators, such as IL-1 and TNF-a [13,14]. Direct or indirect oxidant stress to the airway epithelium and alveolar macrophages may also generate cytokines, such as TNF-a and IL-1b, which in turn can activate airway epithelial cells to induce pro-inflammatory genes, such as TNF-a, IL-8, IL-1, iNOS, COX-2, ICAM-1, VCAM-1, IL-6, MMP-9, MIP-1a, GM-CSF, stress response genes, and antioxidant enzymes (such as MnSOD and thioredoxin) [13]. The genes for these inflammatory mediators are regulated by redox-sensitive transcription factors, including AP-1 and NF-kB. Acetylation of histones has been

583

associated with the transcription of a range of inflammatory mediators. 4. Oxidative stress-induced signal transduction Redox signaling involves at least one reaction of reversible oxidation of a signaling molecule that is intended to modulate a signaling pathway. Oxidative stress is characterized as a decrease in the antioxidant/oxidant ratio, tilted toward a higher proportion of oxidants. Under pathological conditions, however, overproduction of ROS in cells may cause permanent changes in signal transduction and gene expression that are typical of disease states. ROS can lead to the activation of various cell signaling components. Examples include the extracellular signal regulated kinases (ERKs), c-jun N-terminal kinases (JNKs), p38 MAPKs, PKC, PI3K/Akt, and growth factor tyrosine kinases receptors pathways, all of which lead to increased inflammatory gene transcription (Fig. 2). ROS thus play a very important physiological role as second messengers. 4.1. Oxidative stress and MAPKs activation MAP kinases (MAPKs) are evolutionarily conserved regulators that mediate signal transduction and play essential roles in various

Fig. 2. General overview of the roles of ROS in respiratory diseases. Pro-inflammatory mediators, such as TNF-a and IL-1b induce ROS generation via NADPH oxidase activation, which in turn initiates the activation of various signaling pathways, including c-Src, PKCs, EGFR, PDGFR, PI3K/Akt, and MAPKs or transcription factors, such as NFkB, AP-1, and HIF-1a and ultimately induces expression of inflammatory target proteins. Moreover, these proteins may induce airway and pulmonary diseases.

584

I.-T. Lee, C.-M. Yang / Biochemical Pharmacology 84 (2012) 581–590

cellular processes, such as cell growth, differentiation, development, cell cycle, survival, and death. There are three main families of MAPKs in mammals (ERKs, JNKs, and p38 MAPKs), whose functions are regulated by activators, inactivators, substrates, and scaffolds, which together form delicate signaling cascades in response to different extracellular or intracellular stimulation. MAPKs-catalysed phosphorylation of substrate proteins functions as a switch to turn on or off the activity of the substrate protein. The substrates include other protein kinases, phospholipases, and transcription factors. During this process of intracellular communication, MAPKs interact with upstream mediators, such as growth factor tyrosine kinases receptors, G-proteins, and ROS. Activation of MAPKs induces a variety of inflammatory genes that are abnormally expressed in respiratory inflammatory diseases, such as asthma. In addition, pro-inflammatory cytokines have been shown to induce inflammatory target proteins, such as ICAM-1 and VCAM-1 expression via NOX/ROS-dependent MAPKs activation in various cell types, including human airway smooth muscle cells [4]. Moreover, inhibition of NADPH oxidase activation and ROS production by various chemicals, such as cobalt protoporphyrin IX [a heme oxygenase (HO)-1 inducer] has been shown to reduce TNF-a-induced MAPKs phosphorylation and subsequent VCAM-1 and ICAM-1 expression in human airway smooth muscle cells [4]. Taken together, these studies demonstrate that NOX/ROS play a key role in mediating MAPKs activation and inflammatory genes expression in response to pro-inflammatory mediators (Fig. 2). 4.2. Oxidative stress and PKC activation Protein kinase C (PKC) is important in many cellular responses in the lung, including permeability, contraction, migration, hypertrophy, proliferation, apoptosis, and secretion. Many strategies have been used to investigate PKC in lung injury. PKC isoforms are being elucidated as an increasingly diverse family of enzymes involved in the downstream signal transduction and cell function in various types of cells. To date, 11 PKC isoforms have been identified; they are grouped according to their molecular structure and mode of activation: conventional PKCs (a, bI, bII, and g), novel PKCs (d, e, m, u, and h), and atypical PKCs (z and i/l). Importantly, PKC contains unique structural features that are susceptible to oxidative modification [8]. The N-terminal regulatory domain contains zinc-binding, cysteine-rich motifs that are readily oxidized by peroxide. When oxidized, the autoinhibitory function of the regulatory domain is compromised and, consequently, cellular PKC activity is stimulated. The C-terminal catalytic domain contains several reactive cysteines that are targets for various antioxidants. Modification of these cysteines reduces cellular PKC activity. Thus, the two domains of PKC respond differently to two different type of agents: oxidants selectively react with the regulatory domain, stimulate cellular PKC. In contrast, antioxidants react with the catalytic domain, inhibit cellular PKC activity. In vitro studies with purified PKC showed that its activity is modulated by H2O2. On the other hand, TNF-a has been shown to regulate expression of adhesion molecules via a ROS-dependent PKCu activation [16]. Interestingly, PKC also has been shown to regulate ROS production in human airway epithelial cells [17]. Thus, in the airway and lung inflammatory diseases, correlation between ROS formation and PKC activation may play a critical role in regulating inflammatory gene transcription (Fig. 2). 4.3. Oxidative stress and PI3K/Akt activation PI3K/Akt is an anti-apoptotic survival pathway and is regulated by a number of receptor-dependent mechanisms that are activated by growth factors and cytokines. They are classified into three families according to their structure and substrate specificity and

are thought to have distinct biological roles. Recent studies suggested that numerous components of the PI3K pathway play a crucial role in the expression and activation of inflammatory mediators, inflammatory cell recruitment, immune cell function, airway remodeling, and corticosteroid insensitivity in chronic inflammatory respiratory diseases. Selective PI3K inhibitors have been developed that reduce inflammation and some characteristics of disease in experimental animal models. Targeting specific PI3K isoforms that may be overexpressed or overactive in diseases should allow for selective treatment of respiratory diseases. Despite limitations in selectivity, the two commercially available PI3K inhibitors, wortmannin and LY294002, have greatly contributed to our understanding of the biological role of PI3K in airway and lung inflammation. ROS induction is often accompanied by activation of PI3K. For example, LY294002 has been shown to reduce chemokine-induced ROS generation in phagocytes [18], which was further confirmed by studies using PI3K knockout mice. It was similarly reported that the ROS accumulation induced by TNF-a, platelet-derived growth factor, or vascular endothelial growth factor in various cell types was reduced when PI3K activity/ activation was blocked by pharmacological or molecular means. Therefore, PI3K seems to be commonly involved in the ROS accumulation induced by cytokines and growth factors. In addition to the role of PI3K in ROS induction, evidence that supports the opposite hierarchical relationship exists between ROS and PI3K. PI3K was activated in response to the exogenous application of H2O2 in various cell types [19]. Moreover, ROS have been shown to regulate Akt phosphorylation [20], and then induce inflammation in various cell types. Collectively, these results indicate that ROS and PI3K/Akt may play key roles in regulating expression of inflammatory proteins in airway and lung inflammation and injury (Fig. 2). 4.4. Oxidative stress and growth factor tyrosine kinase receptors A variety of cytokines and growth factors that bind to receptors of different classes have been reported to produce ROS in nonphagocytic cells. Growth factor tyrosine kinase receptors play a key role in the transmission of information from outside the cell into the cytoplasm and nucleus [21]. ROS production results from the activation of signaling through the epidermal growth factor (EGF), platelet-derived growth factor (PDGF), and vascular endothelial growth factor (VEGF) receptors [21]. Moreover, ROS induce VEGF expression in vitro and in vivo. In addition, ROS have been shown to stimulate PDGFRa activation via c-Src family kinases [22]. There is accumulating evidence that PKC-dependent phosphorylation of p47phox is essential for PDGF-stimulated ROS generation and NOX/ ROS, which is important for PDGF-induced MAPKs activation [23]. Taken together, these studies suggest that growth factor tyrosine kinase receptors may also play a key role in mediating expression of inflammatory genes through NOX/ROS (Fig. 2). 4.5. Oxidative stress and Src family kinases Src family kinases (SFKs) are signaling enzymes that have long been recognized to regulate critical cellular processes, such as proliferation, survival, migration, and metastasis. Src is activated by binding to growth factor receptors and integrins; cellular stress, including increased ROS; and alterations in phosphatase activity. Moreover, we reported that TNF-a or IL-1b induces VCAM-1 and ICAM-1 expression via a c-Src-dependent NOX/ROS pathway in human airway smooth muscle cells [4,7]. In addition, c-Src has been shown to regulate COX-2/PGE2/IL-6-dependent airway inflammation via NOX/ROS [24]. In addition to the role of c-Src in ROS induction, evidence that supports the opposite hierarchical relationship exists between ROS and c-Src. We recently reported

I.-T. Lee, C.-M. Yang / Biochemical Pharmacology 84 (2012) 581–590

that MMP-9 induction was regulated through a ROS-c-Src signaling pathway [25]. These results suggest that ROS/c-Src or c-Src/ROS play a critical role in regulating airway and lung inflammation. 4.6. Oxidative stress and NF-kB The NF-kB/Rel family complex is a redox-sensitive transcription factor composed of several key regulatory molecules controlling expression of many inflammatory genes [9]. NF-kB usually exists as a heterodimeric complex of p50 and p65/RelA subunits. In unstimulated cells NF-kB is found in the cytoplasm as an inactive non-DNA-binding form, associated with an inhibitor protein called inhibitory kB (IkB) which masks the nuclear translocation signal and so prevents NF-kB from entering the nucleus. Upon cell stimulation with various NF-kB inducers, IkBa is rapidly phosphorylated on two serine residues, which targets the inhibitor protein for ubiquination by the E3 ubiquitin-ligases (E3RSIkB) and subsequent degradation by the 26S proteasome [9]. The released NF-kB dimer can then be translocated into the nucleus and activate target genes by binding with high affinity to kB elements in their promoters. NF-kB is activated by numerous extracellular stimuli, including cytokines such as TNF-a and IL-1b, viruses and environmental particulates (PM10s), and oxidative stress. The role of ROS in the activation of NF-kB signal transduction was initially observed in cells treated with H2O2. Exogenous H2O2 also activated NF-kB in a murine model of ROSinduced acute lung injury (ALI). In a recent study, a murine model of asthma was used to evaluate the effect of the antioxidant, OTC (L-2-oxothiazolidine-4-carboxylate), on inflammation of the airways [26]. Administration of OTC resulted in significant reduction of NF-kB translocation into the nucleus and expression of adhesion molecules, chemokines, and cytokines. These results showed that OTC inhibited NF-kB activity by preventing ROS-induced translocation of this transcription factor into the nucleus. Previous study also reported that antioxidant N-acetylcysteine (NAC) inhibits mucin synthesis and pro-inflammatory mediators in alveolar type II epithelial cells infected with influenza virus A and B and with respiratory syncytial virus (RSV) via NF-kB inhibition [27]. A novel cyclin-dependent kinase inhibitor (BAI) has been shown to downregulate TNF-a-induced expression of cell adhesion molecules by inhibition of NF-kB activation in human pulmonary epithelial cells [28]. Recently, we also demonstrated that overexpression of HO-1 protects against TNF-a-mediated airway inflammation by downregulation of TNFR1-dependent oxidative stress and NF-kB activation [4]. Taken together, these results show that NOX/ROS play a key role in mediating NF-kB activation and the expression of inflammatory proteins in airway and lung inflammation and injury (Fig. 2). 4.7. Oxidative stress and hypoxia-inducible factor-1 Hypoxia-inducible factor (HIF)-1, a heterodimeric basic helixloop-helix-PAS domain transcription factor, is known to activate hypoxia-responsive genes, including VEGF which is one of the major determinants of asthma [8]. HIF-1 is composed of two subunits, HIF-1a and HIF-1b. Whereas the b-subunit protein is constitutively expressed, the stability of the a-subunit and its transcriptional activity are precisely controlled by the intracellular oxygen concentration. Cadmium has been shown to increase HIF-1 and VEGF expression through ROS, ERK, and AKT signaling pathways and induce malignant transformation of human bronchial epithelial cells [29]. Previous study also reported that a novel thiol compound, N-acetylcysteine amide (AD4), attenuates airway inflammation and hyperresponsiveness by regulating activation of NF-kB and HIF-1a as well as reducing ROS generation

585

in allergic airway diseases [30]. Exposure to H2O2 increased HIF-1a protein levels in the lungs, but HIF-1a protein levels were significantly decreased by the administration of OTC and a-lipoic acid, suggesting that exogenous H2O2 also regulates HIF-1a pathway [31]. Collectively, these results indicate that ROS may mediate the expression of inflammatory target proteins in response to pro-inflammatory mediators via a HIF-1a signaling (Fig. 2). 4.8. Oxidative stress and activator protein-1 Activator protein-1 (AP-1) is a sequence-specific transcriptional activator mainly composed of members of the Jun and Fos families. These proteins, which belong to the bZIP group of DNA binding proteins, associate to form a variety of homo and heterodimers that bind to a common site. AP-1 has been shown to be involved in oxidant signaling [8]. Oxidants also induce AP-1 and AP-1dependent gene expression. A number of studies suggest that AP-1 is involved in the pathogenesis of hyperoxic inflammatory lung injury (Fig. 2). In addition, a number of studies have demonstrated that both O2 and H2O2 induce the expression of Jun and Fos proteins, and ROS have also been implicated in the activation of AP-1 by ionizing radiation [32]. Recently, kim et al. demonstrated that apocynin (a NOX inhibitor) shows potential antioxidant activities and inhibitory effects on the activation of redox-sensitive transcription factors, such as NF-kB and AP-1, induced by pro-inflammatory stimuli, such as TNF-a [33]. Thus, these results indicate that ROS play a key role in regulating AP-1 activation (Fig. 2). 4.9. Oxidative stress and histone modifications Histones are subjected to an enormous number of posttranslational modifications, including acetylation, methylation, ubiquitination, sumoylation, and phosphorylation. Histone acetylation plays an important role in the regulation of pro-inflammatory genes expression. In resting cells, DNA is tightly compacted to prevent access of transcription factors. Upon activation by stimuli, DNA is made less compact and available to transcription factors through histone acetylation. Histone acetylation is reversible and is regulated by a group of acetyltransferases (HATs) which promote acetylation, and deacetylases (HDACs) which promote deacetylation. The nuclear receptor co-activators, steroid receptor coactivator 1 (SRC-1), cyclic AMP response element binding (CREB)binding protein (CBP)/adenoviral protein E1A (p300) protein, CBP/ p300 associated factor (P/CAF), and ATF-2, all possess intrinsic HAT activity [8,34]. Of these, the master phosphoprotein CBP/p300 and ATF-2, which are regulated by MAPK pathways, are vital for the coactivation of several transcription factors, including NF-kB and AP1 in the transcription machinery. ROS and TNF-a increase the activation of AP-1 and NF-kB, and regulate chromatin remodeling leading to IL-8 expression in lung cells [35]. IL-8 is a chemokine released during inflammation and is important in the recruitment and activation of immune and inflammatory cells. In addition, ROS, such as H2O2, as well as TNF-a, have been shown to increase histone acetylation in alveolar epithelial cells. Oxidants may also play an important role in the modulation of HDAC activity. Thus, oxidant stress may result in an imbalance between histone acetylation and deacetylation, which may amplify airway and lung inflammation. This may be a potential mechanism for the chronic inflammatory responses which occur in the development of chronic inflammatory airway and lung diseases. In addition, targeted acetylation of histone and/or increased deacetylation may represent a potential novel therapeutic intervention in inflammation. Further understanding of the effects and roles of ROS in basic cellular functions such as amplification of pro-inflammatory and

586

I.-T. Lee, C.-M. Yang / Biochemical Pharmacology 84 (2012) 581–590

immunological responses, signaling pathways, activation of transcription factors (such as NF-kB and AP-1), chromatin modeling (histone acetylation and deacetylation), and gene expression will provide important information regarding basically pathological processes contributing to chronic pulmonary inflammatory diseases. 5. NADPH oxidase/ROS and respiratory inflammatory diseases ROS-mediated damage is thought to be important in the pathogenesis of respiratory inflammatory diseases, such as asthma, COPD, ALI, and pulmonary fibrosis, and NOXs are thought to be a relevant source of ROS in this context. In the following section, we briefly discuss investigations on exacerbation of these important airway and pulmonary diseases caused by ROS. 5.1. NADPH oxidase/ROS and asthma Asthma is a syndrome characterized by the presence of two physiological characteristics, reversible airflow limitation and airway hyperresponsiveness. The role of oxidative stress in asthma is gaining increasing scientific attention. The hallmark of asthma is airway inflammation. Oxidative stress may initiate and augment inflammation, and may also result from inflammation. Patients with asthma demonstrate increased generation of ROS, such as superoxide anion, hydrogen peroxide, and hydroxyl radicals. Increased production of ROS has been demonstrated by many cell types within the lung in asthma, including macrophages, antigenpresenting cells (APCs), neutrophils, and eosinophils [8,9]. Excessive production of ROS correlates with the degree of airway hyperresponsiveness, as quantified by methacholine challenge. ROS are involved in airway smooth muscle contraction, impairment of b-adrenergic receptor function, decreased numbers and function of epithelial cilia, increased mucus production, altered release of inflammatory mediators, influx of inflammatory cells and increased vascular permeability. ROS cause direct contraction of airway smooth muscle preparations and this effect is enhanced when the epithelium is injured or removed. Overproduction of ROS or depression of the protective system also results in bronchial hyperreactivity which is characteristic of asthma [36]. On the other hand, ROS appear to directly stimulate histamine release from mast cells and mucus secretion from airway epithelial cells. Increased generation of ROS can result in direct oxidant damage and shedding of epithelial cells. Previous studies have demonstrated that ROS can contribute to endothelial barrier dysfunction and increased permeability to fluid, macromolecules and inflammatory cells [8,9].

patients, compared with those of non-smokers, can generate ROS via the NOX system. This increase in inflammatory cell number in the lung tissue of COPD becomes compartmentalized depending on cell types. In addition, oxidative stress also contributes to a proteinase-antiproteinase imbalance, both by inactivating antiproteinases, such as a1-antitrypsin and secretory leukocyte proteinase inhibitor, and by activating proteinases, such as MMPs [38]. On the other hand, oxidants also promote inflammation by activating NF-kB or AP-1, which orchestrates the expression of multiple inflammatory genes recognized to be important in COPD, such as TNF-a. Finally, oxidative stress may contribute to reversible airway narrowing. H2O2 constricts airway smooth muscle in vitro and isoprostane F2a-III, formed by free radical peroxidation of arachidonic acid, is a biomarker of lung oxidative stress in vivo, and a potent constrictor of human airways [39]. Therefore, oxidative stress plays a key role in regulating COPD formation through the expression of various inflammatory genes (Fig. 2). 5.3. NADPH oxidase/ROS and acute lung injury It is well known that oxidant production within lung can lead to ALI and sometimes progressive lung injury which often results in irreversible fibrosis. The sources of oxidants may be extrinsic or intrinsic. Intrinsically generated oxidants may be derived from mitochondria, but the most important source of damaging oxidants is phagocytic cells (residential macrophages and recruited neutrophils) that can generate toxic oxygen metabolites from assembly on cell surfaces of NOX (also known as NOX2). Similar pathways leading to oxidant generation can occur in endothelial and alveolar epithelial cells, but the majority of oxidants in lung arises from stimulated phagocytic cells [8,9]. Moreover, lung injury due to hyperoxia is a commonly used model for the study of ALI in animals. The requirement by many patients with ALI for a high fraction of inspired oxygen (FiO2) may predispose to oxidative stress [8]. Zhang et al. indicated that matrine (one of the main active components of Chinese herb Sophora flavescens Ait) exhibits a protective effect on LPSinduced ALI by inhibiting of the inflammatory responses, which may involve the suppression of ROS and tissue oxidative stress [40]. In addition, Qiu et al. also demonstrated that hydrogen inhalation ameliorates LPS-induced ALI and it may exert its protective role by preventing the activation of ROS-JNK-caspase-3 pathway [41]. Recently, phagocytic NOX-ROS signaling has been shown to play a critical role in promoting TNF-a-induced, NF-kBdependent acute inflammatory responses and tissue injury specifically in the lungs, which is effected by preferential leukocyte infiltration [42].

5.2. NADPH oxidase/ROS and COPD 5.4. NADPH oxidase/ROS and lung cancer COPD is characterized by progressive inflammation in the small airways and lung parenchyma, and this is mediated by the increased expression of multiple inflammatory genes, such as COX2, VCAM-1, and ICAM-1. Moreover, markers of oxidative stress have been found in the epithelial lining fluid, breath and urine of cigarette smokers, and patients with COPD [8]. ROS have been shown to react with a variety of biological molecules, including proteins, lipids, and nucleic acids, and this can lead to cell dysfunction or death, as well as damage to the lung extracellular matrix. The oxidant burden in the lungs is enhanced in smokers by the release of ROS from macrophages and neutrophils [37]. Oxidants present in cigarette smoke can stimulate alveolar macrophages to produce ROS and to release a host of mediators, some of which attract neutrophils and other inflammatory cells into the lungs. Both neutrophils and macrophages, which are known to migrate in increased numbers into the lungs of COPD

Lung cancer is a leading cause of cancer mortality worldwide. A lack of clinical symptoms in early-stage disease frequently leads to diagnosis at a late stage, and a 15% 5-year survival rate in all patients so diagnosed. ROS have been suggested to stimulate oncogenes, such as Jun and Fos. Overexpression of Jun is directly associated with lung cancer. The tumorigenic potential of NOX enzymes was first demonstrated with athymic murine models. NOX1-transfected cells produce phenotypically aggressive tumors in athymic mice [43]. In a similar murine model, injection of NOX1expressing cells resulted in rapid cell growth and tumor formation, whereas injection of cells coexpressing NOX1 and catalase failed to promote a mitogenic response or tumor formation in vivo [44]. In addition, in lung cancers, p53, which is associated with the generation of ROS, is often mutated and defective in inducing apoptosis. When mutated, p53 accumulates in the cytoplasm and

I.-T. Lee, C.-M. Yang / Biochemical Pharmacology 84 (2012) 581–590

587

functions as an oncogene. Recent evidence also indicates a role for epigenetic mechanisms in the regulation of NOX/DUOX enzymes in cancer cells. DUOX1 and DUOX2 and their maturation factors were found to be down-regulated by promoter methylation in primary lung carcinomas [45]. Caramori et al. indicated that DNA damage/repair imbalance may contribute to increased risk of lung carcinoma in COPD [46]. Thus, oxidative stress also plays a critical role in mediating lung cancer progression (Fig. 2). 5.5. NADPH oxidase/ROS and pulmonary fibrosis Idiopathic pulmonary fibrosis (IPF) is a chronic progressive disorder in which excessive deposition of extracellular matrix leads to irreversible scarring of interstitial lung tissue. The etiology of IPF remains unknown, but growing evidence suggests that disequilibrium in oxidant/antioxidant balance significantly contributes [9,10]. IPF is currently regarded as a fibroproliferative disorder triggered by repeated alveolar epithelial cell injury. Oxidative stress plays a role in many processes involved in alveolar epithelial cell injury and fibrogenesis (Fig. 2). Damage to the alveolar epithelium is thought to initiate the fibrotic response, but the source of the initial epithelial injury is unknown. Phagocytic cells and a variety of nonphagocytic cells produce ROS via NOX or other oxidases, such as cytochrome P450 and lipoxygenase [15]. The ROS produced can damage cellular macromolecules (DNA, lipids, and proteins). Although fibrosis may occur with very little inflammation as in the case of IPF, other evidence suggests that inflammatory cells may contribute to epithelial injury [47]. Conversely, myofibroblasts from IPF patients produce high levels of H2O2 in response to cytokines and growth factors [48]. ROS produced by these differentiated fibroblasts may be a central source of oxidant stress and cause damage to the overlying epithelium, even in the absence of inflammation. Therefore, sustained exposure to ROS from exogenous or endogenous sources may cause a direct injury to the alveolar epithelium, leading to fibrosis. On the other hand, MMPs and tissue inhibitors of matrix metalloproteinases (TIMPs) play a key role in homeostasis and normal turnover of the extracellular matrix. In IPF, oxidation of the cysteine switch of MMPs may upset the protease/antiprotease balance by activating the latent forms of MMPs. In addition to activating MMPs, ROS can stimulate MMPs transcription. Cui et al. indicated that oxidative stress contributes to the induction and persistence of TGF-b1 induced pulmonary fibrosis [49]. Carnesecchi et al. also demonstrated that NOX4 plays a key role in epithelial cell death during development of lung fibrosis [50]. Recently, epigallocatechin-3-gallate (EGCG) has been shown to augment antioxidant activities and inhibits inflammation during bleomycin-induced experimental pulmonary fibrosis through Nrf2-Keap1 signaling [51]. Thus, NOX/ROS play a critical role during development of lung fibrosis (Fig. 2).

Fig. 3. The imbalance between pro-inflammatory and antioxidant protective genes in inflammation. In inflammation, the balance appears to be tipped in favor of increased pro-inflammatory mediators, due to either release of inflammatory mediators or amplification of the pro-inflammatory effects. Induction of antioxidant protective genes may be a delayed response and decline sharply. MMP-9: matrix metalloproteinase-9; ICAM-1: intercellular adhesion molecule-1; VCAM-1: vascular cell adhesion molecule-1; COX-2: cyclooxygenase-2; cPLA2: cytosolic phospholipase A2; HO-1: heme oxygenase-1; SOD: superoxide dismutase; GPx: glutathione peroxidase.

role in the pathogenesis of airway and lung diseases. In addition, development of such novel antioxidant compounds would be therapeutically useful in monitoring the oxidative and inflammatory biomarkers in the progression/severity of airway and lung diseases, such as COPD and asthma. 6.1. Vitamins C and E Reports of clinical benefit in airway and lung diseases for increased vitamins C and E and other dietary antioxidants have been varied. Previous studies have shown that there are decreased vitamins C and E, b-carotene, and selenium levels in cigarette smokers and that dietary antioxidant intake is an important cofactor in the development of airway and lung diseases. One small trial has shown that there was a clinical improvement in asthmatic symptoms after being given selenium supplementation compared to placebo [52]. In addition, vitamin E has been shown to downmodulate MAPKs, NF-kB, IL-8, VCAM-1, and ICAM-1 in lung epithelial cells induced by TNF-a [53]. Morita et al. indicated that vitamin E treatment prior to injury largely prevents the increase in pulmonary permeability index and moderates the increase in lung lymph flow, increases the PaO2/FiO2 ratio, ameliorates both peak and pause airway pressure increases, and decreases plasma conjugated dienes and nitrotyrosine [54].

6. Roles of antioxidants in the treatment of airway and lung diseases

6.2. Edaravone (MCI-186)

Inflammatory airway and lung diseases are characterized by chronic inflammation and oxidant/antioxidant imbalance, a major cause of cell damage. The development of an oxidant/antioxidant imbalance in airway and lung inflammation may activate redoxsensitive transcription factors, such as AP-1, NF-kB, and HIF-1a, which mediate the expression of genes for pro-inflammatory mediators and protective antioxidants (Fig. 3). Thus, antioxidants that have good bioavailability or molecules that have antioxidant enzyme activity are therefore therapies that not only protect against the direct injurious effects of oxidants, but also may fundamentally alter the inflammatory events which have a central

Edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one), a novel radical scavenger protects neurons by reducing endothelial injury and by ameliorating neuronal damage caused by brain ischemia. Edaravone was found to have promising antioxidant effects: it quenches hydroxyl radical (OH) and inhibits OH-dependent and  OH-independent lipid peroxidation [55]. Edaravone exerts inhibitory effects on both water-soluble and lipid-soluble peroxyl radical-induced peroxidation systems. Its effects are, therefore, similar to the combined effects of vitamins C and E. Moreover, Zhi et al. showed that edaravone decreases interstitial edema and inflammatory cell infiltration as well as prevents the process of

588

I.-T. Lee, C.-M. Yang / Biochemical Pharmacology 84 (2012) 581–590

pulmonary fibrosis [56]. Edaravone has been shown to inhibit lung injury and fibrosis via the repression of lipid hydroperoxide production and the elevation of prostaglandin E2 production in the present experimental murine system [57]. Thus, edaravone may protect against airway and lung diseases, probably through its antioxidant and anti-inflammatory effects. 6.3. N-acetylcysteine NAC is a free radical scavenger and might access the endothelial cell thus increasing intracellular glutathione (GSH) stores. NAC exhibits direct and indirect antioxidant properties. Its free thiol group is capable of interacting with the electrophilic groups of ROS. This interaction with ROS leads to intermediate formation of NAC thiol, with NAC disulphide as a major end product. NAC exerts an indirect antioxidant effect related to its role as a GSH precursor. GSH is a tripeptide made up of glutamic acid, cysteine and glycine. It serves as a central factor in protecting against internal toxic agents (cellular aerobic respiration or metabolism of phagocytes) and external agents (NO, sulphur oxide and other components of cigarette smoke, and pollution). The sulphydryl group of cysteine neutralizes these agents. Maintaining adequate intracellular levels of GSH is essential for overcoming the harmful effects of toxic agents. Treatment with NAC may alter lung oxidant/antioxidant imbalance. NAC (600 mg/ day) given orally increased lung lavage GSH levels [58], reduced ROS production by alveolar macrophages [59] and decreased BALF PMN chemiluminescence in vitro [60]. Recently, Mata et al. indicated that NAC inhibits mucin synthesis and pro-inflammatory mediators in alveolar type II epithelial cells infected with influenza virus A and B and with respiratory syncytial virus (RSV) [27]. However, a newly developed antioxidant, small molecular weight thiol compound, AD4 has been shown to increase cellular levels of GSH and to attenuate oxidative stress related disorders, such as Alzheimer’s disease, Parkinson’s disease, and multiple sclerosis [61]. Lee et al. demonstrated that AD4 attenuates airway inflammation and hyperresponsiveness by regulating activation of NF-kB and HIF-1a as well as reducing ROS generation in allergic airway diseases [30].

6.5. Resveratrol Numerous studies have shown the effectiveness of polyphenols in limiting the progression of chronic diseases. This is likely to occur, at least in part, because of the antioxidant capacity of these molecules, which extends from the availability of hydroxyl groups and the presence of conjugated double bonds. It is likely that resveratrol acts by a variety of antioxidative mechanisms, including inhibiting production of ROS by inflammatory cells, scavenging free radicals, and stimulating biosynthesis of endogenous antioxidants by mechanisms, such as stimulation of nuclear erythroid-related factor (Nrf2) activity [67]. Resveratrol has been reported to increase antioxidant capacity and reduce various markers of oxidative stress. Recently, Lee et al. indicated that resveratrol inhibits the activation of NF-kB (p65) by TNF-a or PMA and reduces ATP-induced mucin secretion from cultured primary rat tracheal surface epithelial (RTSE) cells [68]. Resveratrol has been shown to reduce ROS generation by reducing overexpression of p47phox and the subsequent increased NOX activity [69]. 6.6. Erdosteine Erdosteine is a thiol antioxidant having mucoactive properties, and the ability to reduce bacterial adhesiveness. This compound was introduced as a mucolytic agent for the treatment of chronic airway and pulmonary diseases. Erdosteine breaks the disulfide bonds of mucus glycoproteins, affecting the physical properties of the mucus, thus leading to increased cough clearance [70]. In addition, erdosteine has been reported to have antioxidant, antiinflammatory, and antibacterial activity [70]. Dal Negro et al. showed that erdosteine at a dose of 600 mg/day proved effective in significantly reducing ROS levels in peripheral blood of stable COPD patients who are current smokers, together with reduction in levels of some chemotactic pro-inflammatory cytokines (IL-6 and IL-8) in their bronchial secretions [71]. Recently, the antiinflammatory properties of erdosteine were confirmed in a study involving COPD subjects, wherein by its ability to reduce the proinflammatory eicosanoids levels [72]. Marabini et al. also indicated that erdosteine is effective in preventing H2O2-induced oxidative stress and DNA damage in A549 cells [73].

6.4. Thioredoxin 6.7. Glutaredoxins The oxidoreductase family of redox sensors, such as thioredoxin (Trx) and redox effector factor-1 (ref-1), has attracted particular interest [62]. Trx, has been shown to play an important role in regulating redox-sensitive signaling pathways, such as NF-kB, AP1, p38 MAPK, and JNK [63]. Trx plays a critical role in inhibiting oxidative stress and inflammatory mediator-induced cellular and tissue injury. It has general intracellular antioxidant activity when up-regulated or overexpressed, protecting against oxidative stress. Trx also can be activated by a variety of stress stimuli, such as hypoxia, lipopolysaccharide, H2O2, microbial infections, and photochemicals. Trx is widely expressed in various cells types, including type II pneumocytes, macrophages, and bronchial epithelial cells. Torii et al. indicated that Trx suppresses airway inflammation by inhibiting MIF production thereby limiting the downstream recruitment of eosinophils to the lung independent of modulating systemic Th1/Th2 immunity [64]. Kobayashi et al. also indicated that Trx is beneficial to reduce allergic inflammation through negative regulation of eosinophil functions and Erk1/2 or p38 MAPK activation and has potential in the treatment of allergic diseases, such as asthma [65]. Recently, Chen et al. demonstrated that recombinant human Trx administration markedly attenuates hyperoxia-induced type II cell injury through reduction of ROS generation, elevation of antioxidant activities and regulation of both MAPK and PI3K-Akt signaling pathways [66].

Glutaredoxins (Glrx) are thiol disulfide oxido-reductases, which possess antioxidant and catalytic functions closely associated with GSH. Glrx1 is a potential redox modulatory protein regulating the intracellular, as well as extracellular homeostasis of glutathionylated proteins and GSH in human lung [74]. Moreover, Glrx1 is implicated in regulation of pro-inflammatory NF-kB signaling. Tracheal epithelial cells of mice deficient in Glrx1 were found to be more sensitive to cigarette smoke (CS)-induced cell death with corresponding increases in protein S-glutathionylation [75]. 7. Conclusions There is now increasing evidence that NOX/ROS are generated by several inflammatory and immune and various structural cells of the airways and lungs (Fig. 1). An imbalance between oxidant and antioxidant in favor of oxidants contributes to the pathogenesis of several inflammatory airway and lung diseases, such as COPD, asthma, ALI, pulmonary fibrosis, and lung cancer. Oxidative stress plays a critical role in inflammatory responses in airway and lung diseases via the up-regulation of redox-sensitive transcription factors (such as AP-1, NF-kB, or HIF-1a) and thereby proinflammatory genes (such as MMP-9, VCAM-1, ICAM-1, COX-2, or cPLA2) expression. Inflammation itself results in oxidative stress

I.-T. Lee, C.-M. Yang / Biochemical Pharmacology 84 (2012) 581–590

in the airways and lungs. Simultaneously, endogenous antioxidant mechanisms are present to attenuate the redox-sensitive inflammatory responses. It is when these two opposing mechanisms are out of balance that a chronic and more severe inflammatory state becomes apparent. The use of antioxidants or other pharmacological agents to boost the endogenous antioxidant systems could be used to redress this imbalance. In so doing, this would provide therapeutic benefit in damping down and curtailing the severity and chronicity of the inflammatory responses in respiratory inflammatory diseases. Thus, NOX/ROS appear to be key regulatory factors in the molecular pathways leading to the induction of airway and lung inflammatory diseases (Fig. 2), and offer potential targets for therapeutic interventions. Future work to understand the detail molecular mechanisms of NOX/ROS-mediated pathophysiological pathways and their control by various antioxidants may aid in the design of novel therapies that target the respective signaling components. Conflict of interest The authors have no any potential conflict interests to disclose. Acknowledgements This work was supported by NSC99-2321-B-182-003, NSC982314-B-182-021-MY3, and NSC98-2320-B-255-001-MY3 from National Science Council, Taiwan; EMRPD1A0831 and EMRPD1A0841 from Ministry of Education, Taiwan; and CMRPG391032, CMRPG381523, CMRPD170493, and CMRPD180372 from Chang Gung Medical Research Foundation, Taiwan. References [1] Rahman I, MacNee W. Oxidative stress and regulation of glutathione in lung inflammation. Eur Respir J 2000;16:534–54. [2] Droge W. Free radicals in the physiological control of cell function. Physiol Rev 2002;82:47–95. [3] Barbieri SS, Zacchi E, Amadio P, Gianellini S, Mussoni L, Weksler BB, et al. Cytokines present in smokers’ serum interact with smoke components to enhance endothelial dysfunction. Cardiovasc Res 2011;90:475–83. [4] Lee IT, Luo SF, Lee CW, Wang SW, Lin CC, Chang CC, et al. Overexpression of HO1 protects against TNF-a-mediated airway inflammation by down-regulation of TNFR1-dependent oxidative stress. Am J Pathol 2009;175:519–32. [5] Lee CW, Lin CC, Lee IT, Lee HC, Yang CM. Activation and induction of cytosolic phospholipase A2 by TNF-a mediated through Nox2, MAPKs, NF-(B, and p300 in human tracheal smooth muscle cells. J Cell Physiol 2011;226:2103–14. [6] Lin CP, Huang PH, Tsai HS, Wu TC, Leu HB, Liu PL, et al. Monascus purpureusfermented rice inhibits tumor necrosis factor-a-induced upregulation of matrix metalloproteinase 2 and 9 in human aortic smooth muscle cells. J Pharm Pharmacol 2011;63:1587–94. [7] Luo SF, Chang CC, Lee IT, Lee CW, Lin WN, Lin CC, et al. Activation of ROS/NF-(B and Ca2+/CaM kinase II are necessary for VCAM-1 induction in IL-1b-treated human tracheal smooth muscle cells. Toxicol Appl Pharmacol 2009;237: 8–21. [8] Park HS, Kim SR, Lee YC. Impact of oxidative stress on lung diseases. Respirology 2009;14:27–38. [9] Rahman I, Adcock IM. Oxidative stress and redox regulation of lung inflammation in COPD. Eur Respir J 2006;28:219–42. [10] Rahman I, Biswas SK, Kode A. Oxidant and antioxidant balance in the airways and airway diseases. Eur J Pharmacol 2006;533:222–39. [11] Bedard K, Krause KH. The NOX family of ROS-generating NADPH oxidases: physiology and pathophysiology. Physiol Rev 2007;87:245–313. [12] Pendyala S, Natarajan V. Redox regulation of Nox proteins. Respir Physiol Neurobiol 2010;174:265–71. [13] Rahman I, MacNee W. Regulation of redox glutathione levels and gene transcription in lung inflammation: therapeutic approaches. Free Radic Biol Med 2000;28:1405–20. [14] Rahman I, Mulier B, Gilmour PS, Watchorn T, Donaldson K, Jeffery PK, et al. Oxidant-mediated lung epithelial cell tolerance: the role of intracellular glutathione and nuclear factor-kB. Biochem Pharmacol 2001;62:787–94. [15] Dikalov S. Cross talk between mitochondria and NADPH oxidases. Free Radic Biol Med 2011;51:1289–301. [16] Phalitakul S, Okada M, Hara Y, Yamawaki H. Vaspin prevents TNF-a-induced intracellular adhesion molecule-1 via inhibiting reactive oxygen speciesdependent NF-kB and PKCu activation in cultured rat vascular smooth muscle cells. Pharmacol Res 2011;64:493–500.

589

[17] Shao MX, Nadel JA. Neutrophil elastase induces MUC5AC mucin production in human airway epithelial cells via a cascade involving protein kinase C, reactive oxygen species, and TNF-a-converting enzyme. J Immunol 2005;175: 4009–16. [18] Ptasznik A, Prossnitz ER, Yoshikawa D, Smrcka A, Traynor-Kaplan AE, Bokoch GM. A tyrosine kinase signaling pathway accounts for the majority of phosphatidylinositol 3,4,5-trisphosphate formation in chemoattractant-stimulated human neutrophils. J Biol Chem 1996;271:25204–07. [19] Angeloni C, Motori E, Fabbri D, Malaguti M, Leoncini E, Lorenzini A, et al. H2O2 preconditioning modulates phase II enzymes through p38 MAPK and PI3K/Akt activation. Am J Physiol Heart Circ Physiol 2011;300:H2196–205. [20] Pan J, Chang Q, Wang X, Son Y, Zhang Z, Chen G, et al. Reactive oxygen speciesactivated Akt/ASK1/p38 signaling pathway in nickel compound-induced apoptosis in BEAS 2B cells. Chem Res Toxicol 2010;23:568–77. [21] Neufeld G, Cohen T, Gengrinovitch S, Poltorak Z. Vascular endothelial growth factor (VEGF) and its receptors. FASEB J 1999;13:9–22. [22] Lei H, Kazlauskas A. Growth factors outside of the platelet-derived growth factor (PDGF) family employ reactive oxygen species/Src family kinases to activate PDGF receptor alpha and thereby promote proliferation and survival of cells. J Biol Chem 2009;284:6329–36. [23] Chen KC, Zhou Y, Xing K, Krysan K, Lou MF. Platelet derived growth factor (PDGF)-induced reactive oxygen species in the lens epithelial cells: the redox signaling. Exp Eye Res 2004;78:1057–67. [24] Lin CC, Lee IT, Yang YL, Lee CW, Kou YR, Yang CM. Induction of COX-2/PGE2/IL6 is crucial for cigarette smoke extract-induced airway inflammation: role of TLR4-dependent NADPH oxidase activation. Free Radic Biol Med 2010; 48:240–54. [25] Yang CM, Lin CC, Lee IT, Lin YH, Yang CM, Chen WJ, et al. Japanese encephalitis virus induces matrix metalloproteinase-9 expression via a ROS/c-Src/PDGFR/ PI3K/Akt/MAPKs-dependent AP-1 pathway in rat brain astrocytes. J Neuroinflammation 2012;9:12. [26] Lee YC, Lee KS, Park SJ, Park HS, Lim JS, Park KH, et al. Blockade of airway hyperresponsiveness and inflammation in a murine model of asthma by a prodrug of cysteine, L-2-oxothiazolidine-4-carboxylic acid. FASEB J 2004;18:1917–9. [27] Mata M, Morcillo E, Gimeno C, Cortijo J. N-acetyl-L-cysteine (NAC) inhibit mucin synthesis and pro-inflammatory mediators in alveolar type II epithelial cells infected with influenza virus A and B and with respiratory syncytial virus (RSV). Biochem Pharmacol 2011;82:548–55. [28] Oh JH, Park EJ, Park JW, Lee J, Lee SH, Kwon TK. A novel cyclin-dependent kinase inhibitor down-regulates tumor necrosis factor-a (TNF-a)-induced expression of cell adhesion molecules by inhibition of NF-kB activation in human pulmonary epithelial cells. Int Immunopharmacol 2010;10: 572–9. [29] Jing Y, Liu LZ, Jiang Y, Zhu Y, Guo NL, Barnett J, et al. Cadmium increases HIF-1 and VEGF expression through ROS, ERK, and AKT signaling pathways and induces malignant transformation of human bronchial epithelial cells. Toxicol Sci 2012;125:10–9. [30] Lee KS, Kim SR, Park HS, Park SJ, Min KH, Lee KY, et al. A novel thiol compound, N-acetylcysteine amide, attenuates allergic airway disease by regulating activation of NF-kB and hypoxia-inducible factor-1a. Exp Mol Med 2007; 39:756–68. [31] Lee KS, Kim SR, Park SJ, Park HS, Min KH, Lee MH, et al. Hydrogen peroxide induces vascular permeability via regulation of vascular endothelial growth factor. Am J Respir Cell Mol Biol 2006;35:190–7. [32] Datta R, Hallahan DE, Kharbanda SM, Rubin E, Sherman ML, Huberman E, et al. Involvement of reactive oxygen intermediates in the induction of c-jun gene transcription by ionizing radiation. Biochemistry 1992;31:8300–6. [33] Kim SY, Moon KA, Jo HY, Jeong S, Seon SH, Jung E, et al. Anti-inflammatory effects of apocynin, an inhibitor of NADPH oxidase, in airway inflammation. Immunol Cell Biol 2011. [34] Rahman I. Oxidative stress, transcription factors and chromatin remodelling in lung inflammation. Biochem Pharmacol 2002;64:935–42. [35] Gilmour PS, Rahman I, Hayashi S, Hogg JC, Donaldson K, MacNee W. Adenoviral E1A primes alveolar epithelial cells to PM10-induced transcription of interleukin-8. Am J Physiol Lung Cell Mol Physiol 2001;281:L598–606. [36] Bowler RP. Oxidative stress in the pathogenesis of asthma. Curr Allergy Asthma Rep 2004;4:116–22. [37] Rahman I, MacNee W. Role of oxidants/antioxidants in smoking-induced lung diseases. Free Radic Biol Med 1996;21:669–81. [38] Tuder RM, Janciauskiene SM, Petrache I. Lung disease associated with a1antitrypsin deficiency. Proc Am Thorac Soc 2010;7:381–6. [39] Kawikova I, Barnes PJ, Takahashi T, Tadjkarimi S, Yacoub MH, Belvisi MG. 8epi-PGF2a, a novel noncyclooxygenase-derived prostaglandin, constricts airways in vitro. Am J Respir Crit Care Med 1996;153:590–6. [40] Zhang B, Liu ZY, Li YY, Luo Y, Liu ML, Dong HY, et al. Antiinflammatory effects of matrine in LPS-induced acute lung injury in mice. Eur J Pharm Sci 2011; 44:573–9. [41] Qiu X, Li H, Tang H, Jin Y, Li W, YuSun PingFeng Sun X, et al. Hydrogen inhalation ameliorates lipopolysaccharide-induced acute lung injury in mice. Int Immunopharmacol 2011;11:2130–7. [42] Zhang WJ, Wei H, Tien YT, Frei B. Genetic ablation of phagocytic NADPH oxidase in mice limits TNFa-induced inflammation in the lungs but not other tissues. Free Radic Biol Med 2011;50:1517–25. [43] Suh YA, Arnold RS, Lassegue B, Shi J, Xu X, Sorescu D, et al. Cell transformation by the superoxide-generating oxidase Mox1. Nature 1999;401:79–82.

590

I.-T. Lee, C.-M. Yang / Biochemical Pharmacology 84 (2012) 581–590

[44] Arnold RS, Shi J, Murad E, Whalen AM, Sun CQ, Polavarapu R, et al. Hydrogen peroxide mediates the cell growth and transformation caused by the mitogenic oxidase Nox1. Proc Natl Acad Sci U S A 2001;98:5550–5. [45] Luxen S, Belinsky SA, Knaus UG. Silencing of DUOX NADPH oxidases by promoter hypermethylation in lung cancer. Cancer Res 2008;68:1037–45. [46] Caramori G, Adcock IM, Casolari P, Ito K, Jazrawi E, Tsaprouni L, et al. Unbalanced oxidant-induced DNA damage and repair in COPD: a link towards lung cancer. Thorax 2011;66:521–7. [47] Cantin AM, North SL, Fells GA, Hubbard RC, Crystal RG. Oxidant-mediated epithelial cell injury in idiopathic pulmonary fibrosis. J Clin Invest 1987; 79:1665–73. [48] Waghray M, Cui Z, Horowitz JC, Subramanian IM, Martinez FJ, Toews GB, et al. Hydrogen peroxide is a diffusible paracrine signal for the induction of epithelial cell death by activated myofibroblasts. FASEB J 2005;19: 854–6. [49] Cui Y, Robertson J, Maharaj S, Waldhauser L, Niu J, Wang J, et al. Oxidative stress contributes to the induction and persistence of TGF-b1 induced pulmonary fibrosis. Int J Biochem Cell Biol 2011;43:1122–33. [50] Carnesecchi S, Deffert C, Donati Y, Basset O, Hinz B, Preynat-Seauve O, et al. A key role for NOX4 in epithelial cell death during development of lung fibrosis. Antioxid Redox Signal 2011;15:607–19. [51] Sriram N, Kalayarasan S, Sudhandiran G. Epigallocatechin-3-gallate augments antioxidant activities and inhibits inflammation during bleomycin-induced experimental pulmonary fibrosis through Nrf2-Keap1 signaling. Pulm Pharmacol Ther 2009;22:221–36. [52] Allam MF, Lucane RA. Selenium supplementation for asthma. CDS Rev 2004;CD003538. [53] Ekstrand-Hammarstrom B, Osterlund C, Lilliehook B, Bucht A. Vitamin E down-modulates mitogen-activated protein kinases, nuclear factor-kB and inflammatory responses in lung epithelial cells. Clin Exp Immunol 2007; 147:359–69. [54] Morita N, Shimoda K, Traber MG, Westphal M, Enkhbaatar P, Murakami K, et al. Vitamin E attenuates acute lung injury in sheep with burn and smoke inhalation injury. Redox Rep 2006;11:61–70. [55] Tanaka M. Pharmacological and clinical profile of the free radical scavenger edaravone as a neuroprotective agent. Nippon Yakurigaku Zasshi 2002; 119:301–8. [56] Zhi Q, Sun H, Qian X, Yang L. Edaravone, a novel antidote against lung injury and pulmonary fibrosis induced by paraquat. Int Immunopharmacol 2011;11:96–102. [57] Tajima S, Bando M, Ishii Y, Hosono T, Yamasawa H, Ohno S, et al. Effects of edaravone, a free-radical scavenger, on bleomycin-induced lung injury in mice. Eur Respir J 2008;32:1337–43. [58] Bridgeman MM, Marsden M, MacNee W, Flenley DC, Ryle AP. Cysteine and glutathione concentrations in plasma and bronchoalveolar lavage fluid after treatment with N-acetylcysteine. Thorax 1991;46:39–42.

[59] Linden M, Wieslander E, Eklund A, Larsson K, Brattsand R. Effects of oral Nacetylcysteine on cell content and macrophage function in bronchoalveolar lavage from healthy smokers. Eur Respir J 1988;1:645–50. [60] Jankowska R, Passowicz-Muszynska E, Medrala W, Banas T, Marcinkowska A. The influence of n-acetylcysteine on chemiluminescence of granulocytes in peripheral blood of patients with chronic bronchitis. Pneumonol Alergol Pol 1993;61:586–91. [61] Amer J, Atlas D, Fibach E. N-Acetylcysteine amide (AD4) attenuates oxidative stress in b-thalassemia blood cells. Biochim Biophys Acta 2008;1780:249–55. [62] Nordman T, Xia L, Bjo¨rkhem-Bergman L, Damdimopoulos A, Nalvarte I, Arne´r ES, et al. Regeneration of the antioxidant ubiquinol by lipoamide dehydrogenase, thioredoxin reductase and glutathione reductase. Biofactors 2003;18:45–50. [63] Xu J, Li T, Wu H, Xu T. Role of thioredoxin in lung disease. Pulm Pharmacol Ther 2012. [64] Torii M, Wang L, Ma N, Saito K, Hori T, Sato-Ueshima M, et al. Thioredoxin suppresses airway inflammation independently of systemic Th1/Th2 immune modulation. Eur J Immunol 2010;40:787–96. [65] Kobayashi N, Yamada Y, Ito W, Ueki S, Kayaba H, Nakamura H, et al. Thioredoxin reduces C–C chemokine-induced chemotaxis of human eosinophils. Allergy 2009;64:1130–5. [66] Chen Y, Chang L, Li W, Rong Z, Liu W, Shan R, et al. Thioredoxin protects fetal type II epithelial cells from hyperoxia-induced injury. Pediatr Pulmonol 2010;45:1192–200. [67] Rahman I. Antioxidant therapeutic advances in COPD. Ther Adv Respir Dis 2008;2:351–74. [68] Lee SY, Lee HJ, Sikder MA, Shin HD, Kim JH, Chang GT, et al. Resveratrol inhibits mucin gene expression, production and secretion from airway epithelial cells. Phytother Res 2011. [69] Lopez-Sepulveda R, Gomez-Guzman M, Zarzuelo MJ, Romero M, Sanchez M, Quintela AM, et al. Red wine polyphenols prevent endothelial dysfunction induced by endothelin-1 in rat aorta: role of NADPH oxidase. Clin Sci (Lond) 2011;120:321–33. [70] Moretti M. Pharmacology and clinical efficacy of erdosteine in chronic obstructive pulmonary disease. Expert Rev Respir Med 2007;1:307–16. [71] Dal Negro RW. Erdosteine: antitussive and anti-inflammatory effects. Lung 2008;186(suppl. 1):S70–3. [72] Dal Negro RW, Visconti M, Tognella S, Micheletto C. Erdosteine affects eicosanoid production in COPD. Int J Clin Pharmacol Ther 2011;49:41–5. [73] Marabini L, Calo R, Braga PC. Protective effect of erdosteine metabolite I against hydrogen peroxide-induced oxidative DNA-damage in lung epithelial cells. Arzneimittelforschung 2011;61:700–6. [74] Shelton MD, Mieyal JJ. Regulation by reversible S-glutathionylation: molecular targets implicated in inflammatory diseases. Mol Cells 2008;25:332–46. [75] Kuipers I, Guala AS, Aesif SW, Konings G, Bouwman FG, Mariman EC, et al. Cigarette smoke targets glutaredoxin 1, increasing s-glutathionylation and epithelial cell death. Am J Respir Cell Mol Biol 2011;45:931–7.