Overexpression of pulmonary extracellular superoxide dismutase attenuates endotoxin-induced acute lung injury

Aerosol Delivery of a Novel Recombinant Modified Superoxide Dismutase Protein Reduces Oxidant Injury and Attenuates Escherichia coli Induced Lung Injury in Rats

Background: Acute respiratory distress syndrome (ARDS) is a life-threatening respiratory failure syndrome with diverse etiologies characterized by increased permeability of alveolar-capillary membranes, pulmonary edema, and acute onset hypoxemia. During the ARDS acute phase, neutrophil infiltration into the alveolar space results in uncontrolled release of reactive oxygen species (ROS) and proteases, overwhelming antioxidant defenses and causing alveolar epithelial and lung endothelial injury. Objectives: To investigate the therapeutic potential of a novel recombinant human Cu-Zn-superoxide dismutase (SOD) fusion protein in protecting against ROS injury and for aerosolized SOD delivery to treat Escherichia coli induced ARDS. Methods: Fusion proteins incorporating human Cu-Zn-SOD (hSOD1), with (pep1-hSOD1-his) and without (hSOD1-his) a fused hyaluronic acid-binding peptide, were expressed in E. coli. Purified proteins were evaluated in in vitro assays with human bronchial epithelial cells and through aerosolized delivery to the lung of an E. coli-induced ARDS rat model. Results: SOD proteins exhibited high SOD activity in vitro and protected bronchial epithelial cells from oxidative damage. hSOD1-his and pep1-hSOD1-his retained SOD activity postnebulization and exhibited no adverse effects in the rat. Pep1-hSOD1-his administered through instillation or nebulization to the lung of an E. coli-induced pneumonia rat improved arterial oxygenation and lactate levels compared to vehicle after 48 hours. Static lung compliance was improved when the pep1-hSOD1-his protein was delivered by instillation. White cell infiltration to the lung was significantly reduced by aerosolized delivery of protein, and reduction of cytokine-induced neutrophil chemoattractant-1, interferon-gamma, and interleukin 6 pro-inflammatory cytokine concentrations in bronchoalveolar lavage was observed. Conclusions: Aerosol delivery of a novel recombinant modified SOD protein reduces oxidant injury and attenuates E. coli induced lung injury in rats. The results provide a strong basis for further investigation of the therapeutic potential of hSOD1 in the treatment of ARDS.

Release of extracellular superoxide dismutase into alveolar fluid protects against acute lung injury and inflammation in Staphylococcus aureus pneumonia

Acute respiratory distress syndrome (ARDS) remains a significant cause of morbidity and mortality in critically ill patients. Oxidative stress and inflammation play a crucial role in the pathogenesis of ARDS. Extracellular superoxide dismutase (EC-SOD) is abundant in the lung and is an important enzymatic defense against superoxide. Human single-nucleotide polymorphism in matrix binding region of EC-SOD leads to the substitution of arginine to glycine at position 213 (R213G) and results in release of EC-SOD into alveolar fluid, without affecting enzyme activity. We hypothesized that R213G EC-SOD variant protects against lung injury and inflammation via the blockade of neutrophil recruitment in infectious model of methicillin-resistant S. aureus (MRSA) pneumonia. After inoculation with MRSA, wild-type (WT) mice had impaired integrity of alveolar-capillary barrier and increased levels of IL-1β, IL-6, and TNF-α in the broncho-alveolar lavage fluid (BALF), while infected mice expressing R213G EC-SOD variant maintained the integrity of alveolar-capillary interface and had attenuated levels of proinflammatory cytokines. MRSA-infected mice expressing R213G EC-SOD variant also had attenuated neutrophil numbers in BALF and decreased expression of neutrophil chemoattractant CXCL1 by the alveolar epithelial ATII cells, compared with the infected WT group. The decreased neutrophil numbers in R213G mice were not due to increased rate of apoptosis. Mice expressing R213G variant had a differential effect on neutrophil functionality-the generation of neutrophil extracellular traps (NETs) but not myeloperoxidase (MPO) levels were attenuated in comparison with WT controls. Despite having the same bacterial load in the lung as WT controls, mice expressing R213G EC-SOD variant were protected from extrapulmonary dissemination of bacteria.

Aerosolized Pulmonary Delivery of mRNA Constructs Attenuates Severity of Escherichia coli Pneumonia in the Rat

Acute respiratory distress syndrome (ARDS), a rapid onset inflammatory lung disease with no effective specific therapy, typically has pathogenic etiology termed pneumonia. In previous studies nuclear factor-κB (NF-κB) inhibitor α super-repressor (IκBα-SR) and extracellular superoxide dismutase 3 (SOD3) reduced pneumonia severity when prophylactically delivered by viral vector. In this study, mRNA coding for green fluorescent protein, IκBα-SR, or SOD3 was complexed with cationic lipid, passed through a vibrating mesh nebulizer, and delivered to cell culture or directly to rats undergoing Escherichia coli pneumonia. Injury level was then assessed at 48 h. In vitro, expression was observed as early as 4 h in lung epithelial cells. IκBα-SR and wild-type IκBα mRNAs attenuated inflammatory markers, while SOD3 mRNA induced protective and antioxidant effects. In rat E. coli pneumonia, IκBα-SR mRNA reduced arterial carbon dioxide (pCO2) and reduced lung wet/dry ratio. SOD3 mRNA improved static lung compliance and alveolar-arterial oxygen gradient (AaDO2) and decreased bronchoalveolar lavage (BAL) bacteria load. White cell infiltration and inflammatory cytokine concentrations in BAL and serum were reduced by both mRNA treatments compared to scrambled mRNA controls. These findings indicate nebulized mRNA therapeutics are a promising approach to ARDS therapy, with rapid expression of protein and observable amelioration of pneumonia symptoms.

Gene Therapy for Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a devastating clinical syndrome that leads to acute respiratory failure and accounts for over 70,000 deaths per year in the United States alone, even prior to the COVID-19 pandemic. While its molecular details have been teased apart and its pathophysiology largely established over the past 30 years, relatively few pharmacological advances in treatment have been made based on this knowledge. Indeed, mortality remains very close to what it was 30 years ago. As an alternative to traditional pharmacological approaches, gene therapy offers a highly controlled and targeted strategy to treat the disease at the molecular level. Although there is no single gene or combination of genes responsible for ARDS, there are a number of genes that can be targeted for upregulation or downregulation that could alleviate many of the symptoms and address the underlying mechanisms of this syndrome. This review will focus on the pathophysiology of ARDS and how gene therapy has been used for prevention and treatment. Strategies for gene delivery to the lung, such as barriers encountered during gene transfer, specific classes of genes that have been targeted, and the outcomes of these approaches on ARDS pathogenesis and resolution will be discussed.

N-Acetylcysteine to Combat COVID-19: An Evidence Review

The novel coronavirus disease (COVID-19) is caused by a virus (SARS-Cov-2) and is known for inducing multisystem organ dysfunction associated with significant morbidity and mortality. Current therapeutic strategies for COVID-19 have failed to effectively reduce mortality rate, especially for elderly patients. A newly developed vaccine against SARS-Cov-2 has been reported to induce the production of neutralizing antibodies in young volunteers. However, the vaccine has shown limited benefit in the elderly, suggesting an age-dependent immune response. As a result, exploring new applications of existing medications could potentially provide valuable treatments for COVID-19. N-acetylcysteine (NAC) has been used in clinical practice to treat critically ill septic patients, and more recently for COVID-19 patients. NAC has antioxidant, anti-inflammatory and immune-modulating characteristics that may prove beneficial in the treatment and prevention of SARS-Cov-2. This review offers a thorough analysis of NAC and discusses its potential use for treatment of COVID-19.

Expression of xenobiotic metabolising enzymes in lungs of horses with or without histological evidence of lower airway inflammation

Mild, moderate and severe equine asthma is a problem for equine welfare. The aetiology of the disease is not known in detail but is likely multi‐factorial. One important factor may be inhaled dust which carries harmful substances which may be bioactivated and thus can lead to local inflammation in the airways. The aim of this study was to investigate gene expression and protein localisation of cytochrome P450 (CYP) enzymes, superoxide dismutase and glutathione‐S‐transferases (GST) involved in bioactivation and detoxification of harmful substances in lungs of horses with or without histological evidence of lower airway inflammation. Significantly lower gene expression of CYP2A13 and GSTM1 was observed in lungs from horses with histological evidence of lower airway inflammation compared with horses without. A higher expression, although not significant, was found for CYP1A1 in horses with histological evidence of lower airway inflammation. There were no differences in gene expression of GSTP1 and SOD3. The proteins were localised in the respiratory epithelium which is of relevance as a defence to local exposure of inhaled harmful substances. In conclusion, our study reports differential gene expression of enzymes involved in bioactivation and detoxification of foreign substances in the lungs of horses with histological evidence of lower airway inflammation compared with horses without.

Understanding Gene Therapy in Acute Respiratory Distress Syndrome

Acute Respiratory Distress Syndrome (ARDS) and its complications remain lifethreatening conditions for critically ill patients. The present therapeutic strategies such as prone positioning ventilation strategies, nitric oxide inhalation, restrictive intravenous fluid management, and extracorporeal membrane oxygenation (ECMO) do not contribute much to improving the mortality of ARDS. The advanced understanding of the pathophysiology of acute respiratory distress syndrome suggests that gene-based therapy may be an innovative method for this disease. Many scientists have made beneficial attempts to regulate the immune response genes of ARDS, maintain the normal functions of alveolar epithelial cells and endothelial cells, and inhibit the fibrosis and proliferation of ARDS. Limitations to effective pulmonary gene therapy still exist, including the security of viral vectors and the pulmonary defense mechanisms against inhaled particles. Here, we summarize and review the mechanism of gene therapy for acute respiratory distress syndrome and its application.

Acute Respiratory Distress Syndrome: Bench-to-Bedside Approaches to Improve Drug Development

Despite 50 years of extensive research, no definite drug is currently available to treat acute respiratory distress syndrome (ARDS), and the supportive therapies remain the mainstay of treatment. To improve drug development for ARDS, researchers need to deeply analyze the “omics” approaches, reevaluate the suitable therapeutic targets, resolve the problems of inadequate animal modeling, develop the strategies to reduce the heterogeneity, and reconsider new therapeutic and analytical approaches for better designs of clinical trials.

Protective Effects of Methane-Rich Saline on Rats with Lipopolysaccharide-Induced Acute Lung Injury

Objective. The aim of this research is to evaluate the protective effects of methane-rich saline (MS) on lipopolysaccharide- (LPS-) induced acute lung injury (ALI) and investigate its potential antioxidative, anti-inflammatory, and antiapoptotic activities. Methods. LPS-induced (20 mg/kg) ALI rats were injected with MS (2 ml/kg and 20 ml/kg) before the initiation of LPS induction. Survival rate was determined until 96 h after LPS was induced. Lung injury was assayed by oxygenation index, lung permeability index (LPI), wet-to-dry weight (W/D), and histology. The cells in the bronchoalveolar lavage fluid (BALF) were counted. Oxidative stress was examined by the level of malondialdehyde (MDA) and superoxide dismutase (SOD). Inflammatory factors including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) in BALF were determined by ELISA. Lung tissue apoptosis was detected by TUNEL staining and western blotting of caspase-3. Results. It was found that methane significantly prolonged the rat survival, decreased the lung W/D ratio and the content of the inflammatory factors, and reduced the amount of caspase-3 and apoptotic index. In addition, MS increased the level of SOD and decreased the level of MDA significantly. Conclusions. MS protects the LPS-challenged ALI via antioxidative, anti-inflammatory, and antiapoptotic effect, which may prove to be a novel therapy for the clinical management of ALI.

Perioperative "remote" acute lung injury: recent update

Perioperative acute lung injury (ALI) is a syndrome characterised by hypoxia and chest radiograph changes. It is a serious post-operative complication, associated with considerable mortality and morbidity. In addition to mechanical ventilation, remote organ insult could also trigger systemic responses which induce ALI. Currently, there are limited treatment options available beyond conservative respiratory support. However, increasing understanding of the pathophysiology of ALI and the biochemical pathways involved will aid the development of novel treatments and help to improve patient outcome as well as to reduce cost to the health service. In this review we will discuss the epidemiology of peri-operative ALI; the cellular and molecular mechanisms involved on the pathological process; the clinical considerations in preventing and managing perioperative ALI and the potential future treatment options.

Paradoxical Roles of Antioxidant Enzymes: Basic Mechanisms and Health Implications

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated from aerobic metabolism, as a result of accidental electron leakage as well as regulated enzymatic processes. Because ROS/RNS can induce oxidative injury and act in redox signaling, enzymes metabolizing them will inherently promote either health or disease, depending on the physiological context. It is thus misleading to consider conventionally called antioxidant enzymes to be largely, if not exclusively, health protective. Because such a notion is nonetheless common, we herein attempt to rationalize why this simplistic view should be avoided. First we give an updated summary of physiological phenotypes triggered in mouse models of overexpression or knockout of major antioxidant enzymes. Subsequently, we focus on a series of striking cases that demonstrate "paradoxical" outcomes, i.e., increased fitness upon deletion of antioxidant enzymes or disease triggered by their overexpression. We elaborate mechanisms by which these phenotypes are mediated via chemical, biological, and metabolic interactions of the antioxidant enzymes with their substrates, downstream events, and cellular context. Furthermore, we propose that novel treatments of antioxidant enzyme-related human diseases may be enabled by deliberate targeting of dual roles of the pertaining enzymes. We also discuss the potential of "antioxidant" nutrients and phytochemicals, via regulating the expression or function of antioxidant enzymes, in preventing, treating, or aggravating chronic diseases. We conclude that "paradoxical" roles of antioxidant enzymes in physiology, health, and disease derive from sophisticated molecular mechanisms of redox biology and metabolic homeostasis. Simply viewing antioxidant enzymes as always being beneficial is not only conceptually misleading but also clinically hazardous if such notions underpin medical treatment protocols based on modulation of redox pathways.

Ghrelin attenuates sepsis-associated acute lung injury oxidative stress in rats

This study investigated the effect of ghrelin on oxidative stress in septic rat lung tissue. Male Sprague-Dawley rats were divided into sham-operation, sepsis, and ghrelin groups. Sepsis was induced by cecal ligation and puncture. Ghrelin was administered intraperitoneally at 3 and 15 h post-operation. Bronchoalveolar lavage was performed to collect alveolar macrophages (AMs). Inducible nitric oxide synthase (iNOS) messenger RNA (mRNA) expression in alveolar macrophages and iNOS protein levels were measured by reverse transcription PCR (RT-PCR) and Western blot. Pulmonary pathology was analyzed and nitrotyrosine expression was examined by immunohistochemistry. Plasma superoxide dismutase (SOD) and lung wet/dry weight were measured. In the sepsis group, iNOS mRNA expression in AMs was 1.33 ± 0.05, 1.44 ± 0.08, and 1.57 ± 0.11 at 6, 12, and 20 h post-surgery, respectively, and were higher compared with the sham-operation group (p<0.05). No increase was observed at longer time points. iNOS mRNA expression in the sepsis group was lower compared with the ghrelin group (2.27 ± 0.37) (p<0.05) at 20 h post-surgery. iNOS protein levels in the ghrelin group (0.87 ± 0.03, p<0.05) were lower than in the sepsis group at 20 h. Ghrelin group pathological scores were lower than in the sepsis group (p<0.05). Plasma SOD was slightly non-significantly decreased in the ghrelin group. No difference was observed in lung wet/dry weight ratios between sepsis and ghrelin groups. iNOS mRNA expression in AMs was elevated between 6 and 20 h after cecal ligation and puncture (CLP), but did not progress. Ghrelin attenuated pulmonary iNOS protein expression and tended to increase plasma SOD activity. Ghrelin suppressed pulmonary nitrosative stress in septic rats, but did not improve lung wet/dry weight ratios.

Aerosol-mediated delivery of AAV2/6-IκBα attenuates lipopolysaccharide-induced acute lung injury in rats

Inhibition of the proinflammatory transcription factor NF-κB has previously been shown to attenuate the inflammatory response in tissue after injury. However, the feasibility and efficacy of aerosolized adeno-associated viral (AAV) vector-delivered transgenes to inhibit the NF-κB pathway are less clear. Initial studies optimized the AAV vector for delivery of transgenes to the pulmonary epithelium. The effect of repeated nebulization on the integrity and transduction efficacy of the AAV vector was then examined. Subsequent in vivo studies examined the efficacy of aerosolized rAAV2/6 overexpressing the NF-κB inhibitor IκBα in a rodent endotoxin-induced lung injury model. Initial in vitro investigations indicated that rAAV2/6 was the most effective vector to transduce the lung epithelium, and maintained its integrity and transduction efficacy after repeated nebulization. In our in vivo studies, animals that received aerosolized rAAV2/6-IκBα demonstrated a significant increase in total IκBα levels in lung tissue relative to null vector-treated animals. Aerosolized rAAV2/6-IκBα attenuated endotoxin-induced bronchoalveolar lavage-detected neutrophilia, interleukin-6 and cytokine-induced neutrophil chemoattractant-1 levels, as well as total protein content, and decreased histologic indices of injury. These results demonstrate that aerosolized AAV vectors encoding human IκBα significantly attenuate endotoxin-mediated lung injury and may be a potential therapeutic candidate in the treatment of acute lung injury.

Biological therapies in the acute respiratory distress syndrome

INTRODUCTION

The acute respiratory distress syndrome (ARDS) is characterised by life-threatening respiratory failure requiring mechanical ventilation, and multiple organ failure. It has a mortality of up to 30 - 45% and causes a long-term reduction in quality of life for survivors, with only approximately 50% of survivors able to return to work 12 months after hospital discharge.

AREAS COVERED

In this review we discuss the complex pathophysiology of ARDS, describe the mechanistic pathways implicated in the development of ARDS and how these are currently being targeted with novel biological therapies. These include therapies targeted against inflammatory cytokines, mechanisms mediating increased alveolar permeability and disordered coagulation, as well as the potential of growth factors, gene therapy and mesenchymal stem cells.

EXPERT OPINION

Although understanding of the pathophysiology of ARDS has improved, to date there are no effective pharmacological interventions that target a specific mechanism, with the only potentially effective therapies to date aiming to limit ventilator-associated lung injury. However, we believe that through this improved mechanistic insight and better clinical trial design, there is cautious optimism for the future of biological therapies in ARDS, and expect current and future biological compounds to provide treatment options to clinicians managing this devastating condition.

Inhibition of pulmonary nuclear factor kappa-B decreases the severity of acute Escherichia coli pneumonia but worsens prolonged pneumonia

Introduction

Nuclear factor (NF)-κB is central to the pathogenesis of inflammation in acute lung injury, but also to inflammation resolution and repair. We wished to determine whether overexpression of the NF-κB inhibitor IκBα could modulate the severity of acute and prolonged pneumonia-induced lung injury in a series of prospective randomized animal studies.

Methods

Adult male Sprague-Dawley rats were randomized to undergo intratracheal instillation of (a) 5 × 10⁹ adenoassociated virus (AAV) vectors encoding the IκBα transgene (5 × 10⁹ AAV-IκBα); (b) 1 × 10¹⁰ AAV-IκBα; (c) 5 × 10¹⁰ AAV-IκBα; or (d) vehicle alone. After intratracheal inoculation with Escherichia coli, the severity of the lung injury was measured in one series over a 4-hour period (acute pneumonia), and in a second series after 72 hours (prolonged pneumonia). Additional experiments examined the effects of IκBα and null-gene overexpression on E. coli-induced and sham pneumonia.

Results

In acute pneumonia, IκBα dose-dependently decreased lung injury, improving arterial oxygenation and lung static compliance, reducing alveolar protein leak and histologic injury, and decreasing alveolar IL-1β concentrations. Benefit was maximal at the intermediate (1 × 10¹⁰) IκBα vector dose; however, efficacy was diminished at the higher (5 × 10¹⁰) IκBα vector dose. In contrast, IκBα worsened prolonged pneumonia-induced lung injury, increased lung bacterial load, decreased lung compliance, and delayed resolution of the acute inflammatory response.

Conclusions

Inhibition of pulmonary NF-κB activity reduces early pneumonia-induced injury, but worsens injury and bacterial load during prolonged pneumonia.

Salivary antigen-5/CAP family members are Cu2+-dependent antioxidant enzymes that scavenge O₂₋. and inhibit collagen-induced platelet aggregation and neutrophil oxidative burst

The function of the antigen-5/CAP family of proteins found in the salivary gland of bloodsucking animals has remained elusive for decades. Antigen-5 members from the hematophagous insects Dipetalogaster maxima (DMAV) and Triatoma infestans (TIAV) were expressed and discovered to attenuate platelet aggregation, ATP secretion, and thromboxane A2 generation by low doses of collagen (<1 μg/ml) but no other agonists. DMAV did not interact with collagen, glycoprotein VI, or integrin α2β1. This inhibitory profile resembles the effects of antioxidants Cu,Zn-superoxide dismutase (Cu,Zn-SOD) in platelet function. Accordingly, DMAV was found to inhibit cytochrome c reduction by O2[Symbol: see text] generated by the xanthine/xanthine oxidase, implying that it exhibits antioxidant activity. Moreover, our results demonstrate that DMAV blunts the luminescence signal of O2[Symbol: see text] generated by phorbol 12-myristate 13-acetate-stimulated neutrophils. Mechanistically, inductively coupled plasma mass spectrometry and fluorescence spectroscopy revealed that DMAV, like Cu,Zn-SOD, interacts with Cu(2+), which provides redox potential for catalytic removal of O2[Symbol: see text]. Notably, surface plasmon resonance experiments (BIAcore) determined that DMAV binds sulfated glycosaminoglycans (e.g. heparin, KD ~100 nmol/liter), as reported for extracellular SOD. Finally, fractions of the salivary gland of D. maxima with native DMAV contain Cu(2+) and display metal-dependent antioxidant properties. Antigen-5/CAP emerges as novel family of Cu(2+)-dependent antioxidant enzymes that inhibit neutrophil oxidative burst and negatively modulate platelet aggregation by a unique salivary mechanism.

Magnetic core-shell nanoparticles for drug delivery by nebulization

BACKGROUND

Aerosolized therapeutics hold great potential for effective treatment of various diseases including lung cancer. In this context, there is an urgent need to develop novel nanocarriers suitable for drug delivery by nebulization. To address this need, we synthesized and characterized a biocompatible drug delivery vehicle following surface coating of Fe3O4 magnetic nanoparticles (MNPs) with a polymer poly(lactic-co-glycolic acid) (PLGA). The polymeric shell of these engineered nanoparticles was loaded with a potential anti-cancer drug quercetin and their suitability for targeting lung cancer cells via nebulization was evaluated.

RESULTS

Average particle size of the developed MNPs and PLGA-MNPs as measured by electron microscopy was 9.6 and 53.2 nm, whereas their hydrodynamic swelling as determined using dynamic light scattering was 54.3 nm and 293.4 nm respectively. Utilizing a series of standardized biological tests incorporating a cell-based automated image acquisition and analysis procedure in combination with real-time impedance sensing, we confirmed that the developed MNP-based nanocarrier system was biocompatible, as no cytotoxicity was observed when up to 100 μg/ml PLGA-MNP was applied to the cultured human lung epithelial cells. Moreover, the PLGA-MNP preparation was well-tolerated in vivo in mice when applied intranasally as measured by glutathione and IL-6 secretion assays after 1, 4, or 7 days post-treatment. To imitate aerosol formation for drug delivery to the lungs, we applied quercitin loaded PLGA-MNPs to the human lung carcinoma cell line A549 following a single round of nebulization. The drug-loaded PLGA-MNPs significantly reduced the number of viable A549 cells, which was comparable when applied either by nebulization or by direct pipetting.

CONCLUSION

We have developed a magnetic core-shell nanoparticle-based nanocarrier system and evaluated the feasibility of its drug delivery capability via aerosol administration. This study has implications for targeted delivery of therapeutics and poorly soluble medicinal compounds via inhalation route.

Increased oxidative stress induces apoptosis in human cystic fibrosis cells

Oxidative stress results in deleterious cell function in pathologies associated with inflammation. Here, we investigated the generation of superoxide anion as well as the anti-oxidant defense systems related to the isoforms of superoxide dismutases (SOD) in cystic fibrosis (CF) cells. Pro-apoptotic agents induced apoptosis in CF but not in control cells that was reduced by treatment with SOD mimetic. These effects were associated with increased superoxide anion production, sensitive to the inhibition of IκB-α phosphorylation, in pancreatic but not tracheal CF cells, and reduced upon inhibition of either mitochondrial complex I or NADPH oxidase. CF cells exhibited reduced expression, but not activity, of both Mn-SOD and Cu/Zn-SOD when compared to control cells. Although, expression of EC-SOD was similar in normal and CF cells, its activity was reduced in CF cells. We provide evidence that high levels of oxidative stress are associated with increased apoptosis in CFTR-mutated cells, the sources being different depending on the cell type. These observations underscore a reduced anti-oxidant defense mechanism, at least in part, via diminished EC-SOD activity and regulation of Cu/Zn-SOD and Mn-SOD expressions. These data point to new therapeutic possibilities in targeting anti-oxidant pathways to reduce oxidative stress and apoptosis in CF cells.