Inhibition of tobacco smoke-induced lung inflammation by a catalytic antioxidant

Disturbance in communication between mitochondrial redox processes and the AMPK/PGC-1α/SIRT-1 axis influences diverse organ symptoms in lupus-affected mice

BACKGROUND

Mechanisms behind multiple organ involvement in lupus, is still an enigma for researchers. Mitochondrial dysfunction and oxidative stress are known to be important aspects in lupus etiology however, their role in lupus organ manifestation is yet to be understood. The present study is based on the understanding of interplay between AMPK/PGC-1α/SIRT-1 axis, mitochondrial complexes, and anti-oxidants levels, which might be involved in lupus organ pathology.

METHODOLOGY

Pristane-induced Balb/c mice lupus model (PIL) was utilised and evaluation of anti-oxidants, mitochondrial complexes, pro-inflammatory cytokines levels, biochemical parameters were performed by standard procedures. Tissues were studied by haematoxylin and eosin staining followed by immunohistochemistry. The AMPK/PGC-1α/SIRT-1 expression was analysed by using qPCR and flowcytometry. Analysis of reactive oxygen species (ROS) among WBCs was performed by using various dyes (DCFDA, Mitosox, JC-1) on flowcytometry.

RESULT

Significant presence of immune complexes (Tissue sections), ANA (Serum), and pro-inflammatory cytokines (plasma), diminished anti-oxidants and altered biochemical parameters depict the altered pathology in PIL which was accompanied by dysregulated mitochondrial complex activity. Differential expression of the AMPK/PGC-1α/SIRT-1 axis was detected in tissue and correlation with mitochondrial and antioxidant activity emerged as negative in PIL group while positive in controls. Close association was observed between ROS, mitochondrial membrane potential, and AMPK/PGC-1α/SIRT-1 axis in WBCs.

CONCLUSION

This study concludes that mitochondria play a dual role in lupus organ pathology, contributing to organ damage while also potentially protecting against damage through the regulation of interactions between antioxidants and the AMPK axis expression.

Musculoskeletal crosstalk in chronic obstructive pulmonary disease and comorbidities: Emerging roles and therapeutic potentials

Chronic Obstructive Pulmonary Disease (COPD) is a multifaceted respiratory disorder characterized by progressive airflow limitation and systemic implications. It has become increasingly apparent that COPD exerts its influence far beyond the respiratory system, extending its impact to various organ systems. Among these, the musculoskeletal system emerges as a central player in both the pathogenesis and management of COPD and its associated comorbidities. Muscle dysfunction and osteoporosis are prevalent musculoskeletal disorders in COPD patients, leading to a substantial decline in exercise capacity and overall health. These manifestations are influenced by systemic inflammation, oxidative stress, and hormonal imbalances, all hallmarks of COPD. Recent research has uncovered an intricate interplay between COPD and musculoskeletal comorbidities, suggesting that muscle and bone tissues may cross-communicate through the release of signalling molecules, known as "myokines" and "osteokines". We explored this dynamic relationship, with a particular focus on the role of the immune system in mediating the cross-communication between muscle and bone in COPD. Moreover, we delved into existing and emerging therapeutic strategies for managing musculoskeletal disorders in COPD. It underscores the development of personalized treatment approaches that target both the respiratory and musculoskeletal aspects of COPD, offering the promise of improved well-being and quality of life for individuals grappling with this complex condition. This comprehensive review underscores the significance of recognizing the profound impact of COPD on the musculoskeletal system and its comorbidities. By unravelling the intricate connections between these systems and exploring innovative treatment avenues, we can aspire to enhance the overall care and outcomes for COPD patients, ultimately offering hope for improved health and well-being.

Airway Smooth Muscle Regulated by Oxidative Stress in COPD

Since COPD is a heterogeneous disease, a specific anti-inflammatory therapy for this disease has not been established yet. Oxidative stress is recognized as a major predisposing factor to COPD related inflammatory responses, resulting in pathological features of small airway fibrosis and emphysema. However, little is known about effects of oxidative stress on airway smooth muscle. Cigarette smoke increases intracellular Ca²⁺ concentration and enhances response to muscarinic agonists in human airway smooth muscle. Cigarette smoke also enhances proliferation of these cells with altered mitochondrial protein. Hydrogen peroxide and 8-isoprostans are increased in the exhaled breath condensate in COPD. These endogenous oxidants cause contraction of tracheal smooth muscle with Ca²⁺ dynamics through Ca²⁺ channels and with Ca²⁺ sensitization through Rho-kinase. TNF-α and growth factors potentiate proliferation of these cells by synthesis of ROS. Oxidative stress can alter the function of airway smooth muscle through Ca²⁺ signaling. These phenotype changes are associated with manifestations (dyspnea, wheezing) and pathophysiology (airflow limitation, airway remodeling, airway hyperresponsiveness). Therefore, airway smooth muscle is a therapeutic target against COPD; oxidative stress should be included in treatable traits for COPD to advance precision medicine. Research into Ca²⁺ signaling related to ROS may contribute to the development of a novel agent for COPD.

Therapeutic Potential of Small Molecules Targeting Oxidative Stress in the Treatment of Chronic Obstructive Pulmonary Disease (COPD): A Comprehensive Review

Chronic obstructive pulmonary disease (COPD) is an increasing and major global health problem. COPD is also the third leading cause of death worldwide. Oxidative stress (OS) takes place when various reactive species and free radicals swamp the availability of antioxidants. Reactive nitrogen species, reactive oxygen species (ROS), and their counterpart antioxidants are important for host defense and physiological signaling pathways, and the development and progression of inflammation. During the disturbance of their normal steady states, imbalances between antioxidants and oxidants might induce pathological mechanisms that can further result in many non-respiratory and respiratory diseases including COPD. ROS might be either endogenously produced in response to various infectious pathogens including fungi, viruses, or bacteria, or exogenously generated from several inhaled particulate or gaseous agents including some occupational dust, cigarette smoke (CS), and air pollutants. Therefore, targeting systemic and local OS with therapeutic agents such as small molecules that can increase endogenous antioxidants or regulate the redox/antioxidants system can be an effective approach in treating COPD. Various thiol-based antioxidants including fudosteine, erdosteine, carbocysteine, and N-acetyl-L-cysteine have the capacity to increase thiol content in the lungs. Many synthetic molecules including inhibitors/blockers of protein carbonylation and lipid peroxidation, catalytic antioxidants including superoxide dismutase mimetics, and spin trapping agents can effectively modulate CS-induced OS and its resulting cellular alterations. Several clinical and pre-clinical studies have demonstrated that these antioxidants have the capacity to decrease OS and affect the expressions of several pro-inflammatory genes and genes that are involved with redox and glutathione biosynthesis. In this article, we have summarized the role of OS in COPD pathogenesis. Furthermore, we have particularly focused on the therapeutic potential of numerous chemicals, particularly antioxidants in the treatment of COPD.

Oxidative Stress in Chronic Obstructive Pulmonary Disease

There is a marked increase in oxidative stress in the lungs of patients with COPD, as measured by increased exhaled 8-isoprostane, ethane, and hydrogen peroxide in the breath. The lung may be exposed to exogenous oxidative stress from cigarette smoking and indoor or outdoor air pollution and to endogenous oxidative stress from reactive oxygen species released from activated inflammatory cells, particularly neutrophils and macrophages, in the lungs. Oxidative stress in COPD may be amplified by a reduction in endogenous antioxidants and poor intake of dietary antioxidants. Oxidative stress is a major driving mechanism of COPD through the induction of chronic inflammation, induction of cellular senescence and impaired autophagy, reduced DNA repair, increased autoimmunity, increased mucus secretion, and impaired anti-inflammatory response to corticosteroids. Oxidative stress, therefore, drives the pathology of COPD and may increase disease progression, amplify exacerbations, and increase comorbidities through systemic oxidative stress. This suggests that antioxidants may be effective as disease-modifying treatments. Unfortunately, thiol-based antioxidants, such as N-acetylcysteine, have been poorly effective, as they are inactivated by oxidative stress in the lungs, so there is a search for more effective and safer antioxidants. New antioxidants in development include mitochondria-targeted antioxidants, NOX inhibitors, and activators of the transcription factor Nrf2, which regulates several antioxidant genes.

Reactive oxygen species modulators in pulmonary medicine

Adapted to effectively capture oxygen from inhaled air and deliver it to all other parts of the body, the lungs constitute the organ with the largest surface area. This makes the lungs more susceptible to airborne pathogens and pollutants that mediate pathologies through generation of reactive oxygen species (ROS). One pathological consequence of excessive levels of ROS production is pulmonary diseases that account for a large number of mortality and morbidity in the world. Of the various mechanisms involved in pulmonary disease pathogenesis, mitochondrial dysfunction takes prominent importance. Herein, we briefly describe the significance of oxidative stress caused by ROS in pulmonary diseases and some possible therapeutic strategies.

Copper Tannic Acid Coordination Nanosheet: A Potent Nanozyme for Scavenging ROS from Cigarette Smoke

The global tobacco epidemic is still a devastating threat to public health. Toxic reactive oxygen species (ROS) in the cigarette smoke cannot be efficiently eliminated by currently available cigarette filters. The resultant oxidative stress causes severe lung injury and further diseases. To tackle this challenge, herein, a novel copper tannic acid coordination (CuTA) nanozyme is reported as a highly active and thermostable ROS scavenger. The CuTA nanozyme exhibits intrinsic superoxide dismutase-like activity, catalase-like activity, and hydroxyl radical elimination capacity. These synergistic antioxidant abilities make the CuTA nanozyme a promising candidate for the improvement of commercial cigarette filters. Mouse model results show that commercial cigarettes loaded with CuTA nanozyme efficiently scavenge ROS in the cigarette smoke, reduce oxidative stress-induced lung inflammation, and minimize the resultant acute lung injury. The developed CuTA nanozyme offers an efficient ROS scavenger with multiple antioxidant ability and opens up new opportunities for the modification of cigarette filters to reduce the toxic effects of cigarette smoke.

Oxidative stress-based therapeutics in COPD

Oxidative stress is a major driving mechanism in the pathogenesis of COPD. There is increased oxidative stress in the lungs of COPD patients due to exogenous oxidants in cigarette smoke and air pollution and due to endogenous generation of reactive oxygen species by inflammatory and structural cells in the lung. Mitochondrial oxidative stress may be particularly important in COPD. There is also a reduction in antioxidant defences, with inactivation of several antioxidant enzymes and the transcription factors Nrf2 and FOXO that regulate multiple antioxidant genes. Increased systemic oxidative stress may exacerbate comorbidities and contribute to skeletal muscle weakness. Oxidative stress amplifies chronic inflammation, stimulates fibrosis and emphysema, causes corticosteroid resistance, accelerates lung aging, causes DNA damage and stimulates formation of autoantibodies. This suggests that treating oxidative stress by antioxidants or enhancing endogenous antioxidants should be an effective strategy to treat the underlying pathogenetic mechanisms of COPD. Most clinical studies in COPD have been conducted using glutathione-generating antioxidants such as N-acetylcysteine, carbocysteine and erdosteine, which reduce exacerbations in COPD patients, but it is not certain whether this is due to their antioxidant or mucolytic properties. Dietary antioxidants have so far not shown to be clinically effective in COPD. There is a search for more effective antioxidants, which include superoxide dismutase mimetics, NADPH oxidase inhibitors, mitochondria-targeted antioxidants and Nrf2 activators.

Conventional and Nanotechnology Based Approaches to Combat Chronic Obstructive Pulmonary Disease: Implications for Chronic Airway Diseases

Chronic obstructive pulmonary disease (COPD) is the most prevalent obstructive lung disease worldwide characterized by decline in lung function. It is associated with airway obstruction, oxidative stress, chronic inflammation, mucus hypersecretion, and enhanced autophagy and cellular senescence. Cigarette smoke being the major risk factor, other secondary risk factors such as the exposure to air pollutants, occupational exposure to gases and fumes in developing countries, also contribute to the pathogenesis of COPD. Conventional therapeutic strategies of COPD are based on anti-oxidant and anti-inflammatory drugs. However, traditional anti-oxidant pharmacological therapies are commonly used to alleviate the impact of COPD as they have many associated repercussions such as low diffusion rate and inappropriate drug pharmacokinetics. Recent advances in nanotechnology and stem cell research have shed new light on the current treatment of chronic airway disease. This review is focused on some of the anti-oxidant therapies currently used in the treatment and management of COPD with more emphasis on the recent advances in nanotechnology-based therapeutics including stem cell and gene therapy approaches for the treatment of chronic airway disease such as COPD and asthma.

Long-Term Sequelae of Smoking and Cessation in Spontaneously Hypertensive Rats

Smoking is a major risk factor for heart attack, stroke, and lung cancer. Tobacco smoke (TS) causes bronchitis, emphysema, persistent cough, and dyspnea. Smoking cessation minimizes risks of TS-related disease. To determine whether smoking cessation could reverse TS-induced pulmonary changes, 10-week-old male spontaneously hypertensive rats were exposed to TS or filtered air (FA) for 39 weeks and allowed to live out their normal lifespan. Significantly (P ≤ .05) decreased survival was noted by 21 months in TS versus FA rats. In TS rats, persistent peribronchiolar, perivascular, alveolar, and subpleural inflammation were observed with pervasive infiltration of pigmented foamy macrophages and plausible intra-alveolar fibrosis and osseous metaplasia. Alveolar airspace was significantly (P ≤ .05) increased in TS versus FA rats as was the volume of stored epithelial mucosubstances in the left central axial airway. Increased mucin contributes to airflow obstruction and increased lung infection risks. Findings suggest TS-induced changes do not attenuate with smoking cessation but result in irreversible damage similar to chronic obstructive pulmonary disease. The observed persistent pulmonary changes mirror common TS effects such as chest congestion, sputum production, and shortness of breath long after smoking cessation and represent important targets for treatment of former smokers.

The potential of lipid-polymer nanoparticles as epigenetic and ROS control approaches for COPD

Chronic obstructive pulmonary disease (COPD) is a lung disease caused by an inflammatory response to various inhaled toxins, especially cigarette smoke. Reactive oxygen species (ROS) and epigenetic abnormality are intimately related to the pathology of COPD, and the overproduction of ROS results in a decrease of histone deacetylase 2 (HDAC2), leading to glucocorticoid resistance. Therefore, a novel treatment that simultaneously reduces ROS level and glucocorticoid resistance is urgently needed. In this study, we developed a codelivery system using core-shell type lipid-polymer nanoparticles (LPNs) composed of a poly(lactic acid) (PLA) core encapsulating a potent antioxidant Mn-porphyrin dimer (MnPD) and a cationic lipid (DOTAP) shell that binds HDAC2-encoding plasmid DNA (pHDAC2), as a new therapeutic approach toward COPD. The transfection of pHDAC2 combined with the elimination of ROS by MnPD exhibited a significant enhancement of intracellular HDAC2 expression levels, suggesting that the multi-antioxidative activity of MnPD plays a crucial role in the expression of HDAC2. Moreover, treatment with LPNs efficiently ameliorated the steroid resistance in COPD models in vitro as evidenced by the lowered expression levels of IL-8. Recovery from mitochondrial dysfunction may be the mechanism underlying the action of LPNs. The PLA-MnPD/DOTAP/pHDAC2 system proposed offers a new therapeutic approach for COPD based on the synergism of ROS elimination and HDAC2 expression.

Premalignant lesions of squamous cell carcinoma of the lung: The molecular make-up and factors affecting their progression

Squamous cell carcinoma (SCC), one of the most common forms of lung cancer, shows accelerated progression and aggressive growth and usually is observed at advanced stages. SCC originates from morphological changes in the bronchial epithelium that occur during chronic inflammation: basal cell hyperplasia, squamous metaplasia, and dysplasia I-III. However, the process is not inevitable; it can be stopped at any stage, remain in the stable state indefinitely and either progress or regress. The reasons and mechanisms of different scenarios of the evolution of premalignant lesions in the respiratory epithelium are not fully understood. In this review, we summarized the literature data (including our own data) regarding genetic, epigenetic, transcriptomic and proteomic profiles of the premalignant lesions and highlighted factors (environmental causes, inflammation, and gene polymorphism) that may govern their progression or regression. In conclusion, we reviewed strategies for lung cancer prevention and proposed new models and research directions for studying premalignant lesions and developing new tools to predict the risk of their malignant transformation.

New frontiers in the treatment of comorbid cardiovascular disease in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a disease characterised by persistent airflow limitation that is not fully reversible and is currently the fourth leading cause of death globally. It is now well established that cardiovascular-related comorbidities contribute to morbidity and mortality in COPD, with approximately 50% of deaths in COPD patients attributed to a cardiovascular event (e.g. myocardial infarction). Cardiovascular disease (CVD) and COPD share various risk factors including hypertension, sedentarism, smoking and poor diet but the underlying mechanisms have not been fully established. However, there is emerging and compelling experimental and clinical evidence to show that increased oxidative stress causes pulmonary inflammation and that the spill over of pro-inflammatory mediators from the lungs into the systemic circulation drives a persistent systemic inflammatory response that alters blood vessel structure, through vascular remodelling and arterial stiffness resulting in atherosclerosis. In addition, regulation of endothelial-derived vasoactive substances (e.g. nitric oxide (NO)), which control blood vessel tone are altered by oxidative damage of vascular endothelial cells, thus promoting vascular dysfunction, a key driver of CVD. In this review, the detrimental role of oxidative stress in COPD and comorbid CVD are discussed and we propose that targeting oxidant-dependent mechanisms represents a novel strategy in the treatment of COPD-associated CVD.

Pathobiological mechanisms underlying metabolic syndrome (MetS) in chronic obstructive pulmonary disease (COPD): clinical significance and therapeutic strategies

Chronic obstructive pulmonary disease (COPD) is a major incurable global health burden and is currently the 4th largest cause of death in the world. Importantly, much of the disease burden and health care utilisation in COPD is associated with the management of its comorbidities (e.g. skeletal muscle wasting, ischemic heart disease, cognitive dysfunction) and infective viral and bacterial acute exacerbations (AECOPD). Current pharmacological treatments for COPD are relatively ineffective and the development of effective therapies has been severely hampered by the lack of understanding of the mechanisms and mediators underlying COPD. Since comorbidities have a tremendous impact on the prognosis and severity of COPD, the 2015 American Thoracic Society/European Respiratory Society (ATS/ERS) Research Statement on COPD urgently called for studies to elucidate the pathobiological mechanisms linking COPD to its comorbidities. It is now emerging that up to 50% of COPD patients have metabolic syndrome (MetS) as a comorbidity. It is currently not clear whether metabolic syndrome is an independent co-existing condition or a direct consequence of the progressive lung pathology in COPD patients. As MetS has important clinical implications on COPD outcomes, identification of disease mechanisms linking COPD to MetS is the key to effective therapy. In this comprehensive review, we discuss the potential mechanisms linking MetS to COPD and hence plausible therapeutic strategies to treat this debilitating comorbidity of COPD.

Acute pulmonary effects of aerosolized nicotine

Nicotine is a highly addictive principal component of both tobacco and electronic cigarette that is readily absorbed in blood. Nicotine-containing electronic cigarettes are promoted as a safe alternative to cigarette smoking. However, the isolated effects of inhaled nicotine are largely unknown. Here we report a novel rat model of aerosolized nicotine with a particle size (~1 μm) in the respirable diameter range. Acute nicotine inhalation caused increased pulmonary edema and lung injury as measured by enhanced bronchoalveolar lavage fluid protein, IgM, lung wet-to-dry weight ratio, and high-mobility group box 1 (HMGB1) protein and decreased lung E-cadherin protein. Immunohistochemical analysis revealed congested blood vessels and increased neutrophil infiltration. Lung myeloperoxidase mRNA and protein increased in the nicotine-exposed rats. Complete blood counts also showed an increase in neutrophils, white blood cells, eosinophils, and basophils. Arterial blood gas measurements showed an increase in lactate. Lungs of nicotine-inhaling animals revealed increased mRNA levels of IL-1A and CXCL1. There was also an increase in IL-1α protein. In in vitro air-liquid interface cultures of airway epithelial cells, there was a dose dependent increase in HMGB1 release with nicotine treatment. Air-liquid cultures exposed to nicotine also resulted in a dose-dependent loss of barrier as measured by transepithelial electrical resistance and a decrease in E-cadherin expression. Nicotine also caused a dose-dependent increase in epithelial cell death and an increase in caspase-3/7 activities. These results show that the nicotine content of electronic cigarettes may have adverse pulmonary and systemic effects.

Antioxidants and Chronic Obstructive Pulmonary Disease

Antioxidants represent an attractive therapeutic avenue for individuals with chronic obstructive pulmonary disease (COPD). Cigarette smoke, the major cause of COPD, contains very high concentrations of gaseous and soluble oxidants that can directly induce cell injury and death. Furthermore, particulate matter in cigarette smoke activates lung macrophages that subsequently attract neutrophils. Both neutrophils and macrophages from the lungs of cigarette smokers continuously release large amounts of superoxide and hydrogen peroxide through the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex. Once individuals with COPD stop smoking, the neutrophilic inflammation in the airways and lung parenchyma persists, as do the markers of oxidative stress. Several animal models of cigarette smoke-induced injury have provided evidence that various antioxidants may prevent inflammation and morphological changes associated with COPD however, evidence of benefit in patients is less abundant. Although oxidants can inactivate alpha-1 antitrypsin and other protective proteins, damage lung tissue, and increase mucus production, they also are essential for killing pathogens and resolving inflammation. This review will examine the pre-clinical and clinical evidence of a role for antioxidants in the therapy of patients with COPD.

Improvements in SOD mimic AEOL-10150, a potent broad-spectrum antioxidant

AEOL-10150 is a broad-spectrum metalloporphyrin superoxidase dismutase (SOD) mimic specifically designed to neutralize reactive oxygen and nitrogen species. Research has shown that AEOL-10150 is a potent medical countermeasure against national security threats including sulfur mustard (SM), nerve agent exposure and radiation pneumonitis following a radiological/nuclear incident sufficient to cause acute radiation syndrome (ARS). AEOL-10150 performed well in animal safety studies, and two completed phase 1 safety studies in patients demonstrated that the drug was safe and well tolerated, indicating that AEOL-10150 has potential as a new catalytic antioxidant drug. In this article, we review improvements in AEOL-10150 in preclinical pharmacodynamic studies, especially regarding anti-SM, chlorine gas and radiation exposure studies.

Ultrafine Particulate Matter Combined With Ozone Exacerbates Lung Injury in Mature Adult Rats With Cardiovascular Disease

Particulate matter (PM) and ozone (O3) are dominant air pollutants that contribute to development and exacerbation of multiple cardiopulmonary diseases. Mature adults with cardiovascular disease (CVD) are particularly susceptible to air pollution-related cardiopulmonary morbidities and mortalities. The aim was to investigate the biologic potency of ultrafine particulate matter (UFPM) combined with O3 in the lungs of mature adult normotensive and spontaneously hypertensive (SH) Wistar-Kyoto rats. Conscious, mature adult male normal Wistar-Kyoto (NW) and SH rats were exposed to one of the following atmospheres: filtered air (FA); UFPM (∼ 250 μg/m3); O3 (1.0 ppm); or UFPM + O3 (∼ 250 μg/m3 + 1.0 ppm) combined for 6 h, followed by an 8 h FA recovery period. Lung sections were evaluated for lesions in the large airways, terminal bronchiolar/alveolar duct regions, alveolar parenchyma, and vasculature. NW and SH rats were similarly affected by the combined-pollutant exposure, displaying severe injury in both large and small airways. SH rats were particularly susceptible to O3 exposure, exhibiting increased injury scores in terminal bronchioles and epithelial degeneration in large airways. UFPM-exposure groups had minimal histologic changes. The chemical composition of UFPM was altered by the addition of O3, indicating that ozonolysis promoted compound degradation. O3 increased the biologic potency of UFPM, resulting in greater lung injury following exposure. Pathologic manifestations of CVD may confer susceptibility to air pollution by impairing normal lung defenses and responses to exposure.

The pathophysiological role of mitochondrial oxidative stress in lung diseases

Mitochondria are critically involved in reactive oxygen species (ROS)-dependent lung diseases, such as lung fibrosis, asbestos, chronic airway diseases and lung cancer. Mitochondrial DNA (mtDNA) encodes mitochondrial proteins and is more sensitive to oxidants than nuclear DNA. Damage to mtDNA causes mitochondrial dysfunction, including electron transport chain impairment and mitochondrial membrane potential loss. Furthermore, damaged mtDNA also acts as a damage-associated molecular pattern (DAMP) that drives inflammatory and immune responses. In this review, crosstalk among alveolar epithelial cells, alveolar macrophages and mitochondria is examined. ROS-related transcription factors and downstream cell signaling pathways are also discussed. We conclude that targeting oxidative stress with antioxidant agents, such as thiol molecules, polyphenols and superoxide dismutase (SOD), and promoting mitochondrial biogenesis should be considered as novel strategies for treating lung diseases that currently have no effective treatment options.

Sex and strain-based inflammatory response to repeated tobacco smoke exposure in spontaneously hypertensive and Wistar Kyoto rats

CONTEXT

Approximately four million people die every year from chronic obstructive pulmonary disease (COPD), with more than 80% of the cases attributed to smoking.

OBJECT

The purpose of this study was to examine the rat strain and sex-related differences and the extended tobacco smoke exposure to induce lung injury and inflammation with the goal of finding a suitable rodent model to study COPD.

METHODS

Male and female spontaneously hypertensive (SH) and male Wistar Kyoto (WKY) rats were exposed to filtered air (FA) or to tobacco smoke (TS: 90 mg/m3 particulate concentration) for 6 h/day, three days/week for 4 or 12 weeks.

RESULTS

Male SH rats demonstrated an enhanced, persistent inflammatory response compared to female SH and male WKY rats with extended TS exposure. Following four weeks of TS exposure, male SH rats had significantly increased total leukocytes and macrophage numbers, levels of TNF-alpha and elevated lactate dehydrogenase activity in bronchoalveolar lavage fluid compared with female SH, male WKY rats and corresponding controls. After 12 weeks of TS exposure, male SH rats continued to show significant increase in inflammatory cells and TNF-alpha, as well as IL-6 mRNA lung expression. In addition, the alveolar airspace of male SH rats exposed to TS was significantly enlarged compared to their FA controls, female SH and WKY rats.

CONCLUSION

The male SH rat demonstrates greater cellular, inflammatory and structural changes highly reminiscent of COPD compared to female SH and male WKY rats, suggesting that the male SH rat is an optimal rodent model to study COPD.

Antioxidant strategies in respiratory medicine

Pulmonary oxidant stress plays an important pathogenetic role in disease conditions including acute lung injury/adult respiratory distress syndrome (ALI/ARDS), hyperoxia, ischemia-reperfusion, sepsis, radiation injury, lung transplantation, COPD, and inflammation. Reactive oxygen species (ROS), released from activated macrophages and leukocytes or formed in the pulmonary epithelial and endothelial cells, damage the lungs and initiate cascades of pro-inflammatory reactions propagating pulmonary and systemic stress. Diverse molecules including small organic compounds (e.g. gluthatione, tocopherol (vitamin E), flavonoids) serve as natural antioxidants that reduce oxidized cellular components, decompose ROS and detoxify toxic oxidation products. Antioxidant enzymes can either facilitate these antioxidant reactions (e.g. peroxidases using glutathione as a reducing agent) or directly decompose ROS (e.g. superoxide dismutases [SOD] and catalase). Many antioxidant agents are being tested for treatment of pulmonary oxidant stress. The administration of small antioxidants via the oral, intratracheal and vascular routes for the treatment of short- and long-term oxidant stress showed rather modest protective effects in animal and human studies. Intratracheal and intravascular administration of antioxidant enzymes are being currently tested for the treatment of acute oxidant stress. For example, intratracheal administration of recombinant human SOD is protective in premature infants exposed to hyperoxia. However, animal and human studies show that more effective delivery of drugs to cells experiencing oxidant stress is needed to improve protection. Diverse delivery systems for antioxidants including liposomes, chemical modifications (e.g. attachment of masking pegylated [PEG]-groups) and coupling to affinity carriers (e.g. antibodies against cellular adhesion molecules) are being employed and currently tested, mostly in animal and, to a limited extent, in humans, for the treatment of oxidant stress. Further studies are needed, however, in order to develop and establish effective applications of pulmonary antioxidant interventions useful in clinical practice. Although beyond the scope of this review, antioxidant gene therapies may eventually provide a strategy for the management of subacute and chronic pulmonary oxidant stress.

Impact of Superoxide Dismutase Mimetic AEOL 10150 on the Endothelin System of Fischer 344 Rats

Endothelin-1 is a potent vasoconstrictor and mitogenic peptide involved in the regulation of vasomotor tone and maintenance of blood pressure. Oxidative stress activates the endothelin system, and is implicated in pulmonary and cardiovascular diseases including hypertension, congestive heart failure, and atherosclerosis. Superoxide dismutase mimetics designed with the aim of treating diseases that involve reactive oxygen species in their pathophysiology may exert a hypotensive effect, but effects on the endothelin system are unknown. Our objective was to determine the effect of the superoxide dismutase mimetic AEOL 10150 on the basal endothelin system in vivo. Male Fischer-344 rats were injected subcutaneously with 0, 2 or 5 mg/kg body weight of AEOL 10150 in saline. Plasma oxidative stress markers and endothelins (bigET-1, ET-1, ET-2, ET-3) as well as lung and heart endothelin/nitric oxide system gene expressions were measured using HPLC-Coularray, HPLC-Fluorescence and RT-PCR respectively. AEOL 10150 reduced (p<0.05) the circulating levels of isoprostane (-25%) and 3-nitrotyrosine (-50%) measured in plasma 2h and 24h after treatment, confirming delivery of a physiologically-relevant dose and the potent antioxidant activity of the drug. The reduction in markers of oxidative stress coincided with sustained 24h decrease (p<0.05) of plasma levels of ET-1 (-50%) and ET-3 (-10%). Expression of preproET-1 and endothelin converting enzyme-1 mRNA were not altered significantly in the lungs. However preproET-1 (not significant) and ECE-1 mRNA (p<0.05) were increased (10-25%) in the heart. Changes in the lungs included decrease (p<0.05) of mRNA for the ET-1 clearance receptor ETB and the vasoconstriction-signaling ETA receptor (-30%), and an early surge of inducible nitric oxide synthase expression followed by sustained decrease (-40% after 24 hours). The results indicate that interception of the endogenous physiological flux of reactive nitrogen species and reactive oxygen species in rats impacts the endothelin/nitric oxide system, supporting a homeostatic relationship between those systems.

Dose Optimization Study of AEOL 10150 as a Mitigator of Radiation-Induced Lung Injury in CBA/J Mice

AEOL 10150 is a catalytic metalloporphyrin superoxide dismutase mimic being developed as a medical countermeasure for radiation-induced lung injury (RILI). The efficacy of AEOL 10150 against RILI through a reduction of oxidative stress, hypoxia and pro-apoptotic signals has been previously reported. The goal of this study was to determine the most effective dose of AEOL 10150 (daily subcutaneous injections, day 1-28) in improving 180-day survival in CBA/J mice after whole-thorax lung irradiation (WTLI) to a dose of 14.6 Gy. Functional and histopathological assessments were performed as secondary end points. Estimated 180-day survival improved from 10% in WTLI alone to 40% with WTLI-AEOL 10150 at 25 mg/kg (P = 0.065) and to 30% at 40 mg/kg (P = 0.023). No significant improvement was seen at doses of 5 and 10 mg/kg or at doses between 25 and 40 mg/kg. AEOL 10150 treatment at 25 mg/kg lowered the respiratory function parameter of enhanced pause (Penh) significantly, especially at week 16 and 18 (P = 0.044 and P = 0.025, respectively) compared to vehicle and other doses. Pulmonary edema/congestion were also significantly reduced at the time of necropsy among mice treated with 25 and 40 mg/kg AEOL 10150 compared to WTLI alone (P < 0.02). In conclusion, treatment with AEOL 10150 at a dose of 25 mg/kg/day for a total of 28 days starting 24 h after WTLI in CBA/J mice was found to be the optimal dose with improvement in survival and lung function. Future studies will be required to determine the optimal duration and therapeutic window for drug delivery at this dose.

Targeting oxidant-dependent mechanisms for the treatment of COPD and its comorbidities

Chronic obstructive pulmonary disease (COPD) is an incurable global health burden and is characterised by progressive airflow limitation and loss of lung function. In addition to the pulmonary impact of the disease, COPD patients often develop comorbid diseases such as cardiovascular disease, skeletal muscle wasting, lung cancer and osteoporosis. One key feature of COPD, yet often underappreciated, is the contribution of oxidative stress in the onset and development of the disease. Patients experience an increased burden of oxidative stress due to the combined effects of excess reactive oxygen species (ROS) and nitrogen species (RNS) generation, antioxidant depletion and reduced antioxidant enzyme activity. Currently, there is a lack of effective treatments for COPD, and an even greater lack of research regarding interventions that treat both COPD and its comorbidities. Due to the involvement of oxidative stress in the pathogenesis of COPD and many of its comorbidities, a unique therapeutic opportunity arises where the treatment of a multitude of diseases may be possible with only one therapeutic target. In this review, oxidative stress and the roles of ROS/RNS in the context of COPD and comorbid cardiovascular disease, skeletal muscle wasting, lung cancer, and osteoporosis are discussed and the potential for therapeutic benefit of anti-oxidative treatment in these conditions is outlined. Because of the unique interplay between oxidative stress and these diseases, oxidative stress represents a novel target for the treatment of COPD and its comorbidities.

A 28-day rat inhalation study with an integrated molecular toxicology endpoint demonstrates reduced exposure effects for a prototypic modified risk tobacco product compared with conventional cigarettes

Towards a systems toxicology-based risk assessment, we investigated molecular perturbations accompanying histopathological changes in a 28-day rat inhalation study combining transcriptomics with classical histopathology. We demonstrated reduced biological activity of a prototypic modified risk tobacco product (pMRTP) compared with the reference research cigarette 3R4F. Rats were exposed to filtered air or to three concentrations of mainstream smoke (MS) from 3R4F, or to a high concentration of MS from a pMRTP. Histopathology revealed concentration-dependent changes in response to 3R4F that were irritative stress-related in nasal and bronchial epithelium, and inflammation-related in the lung parenchyma. For pMRTP, significant changes were seen in the nasal epithelium only. Transcriptomics data were obtained from nasal and bronchial epithelium and lung parenchyma. Concentration-dependent gene expression changes were observed following 3R4F exposure, with much smaller changes for pMRTP. A computational-modeling approach based on causal models of tissue-specific biological networks identified cell stress, inflammation, proliferation, and senescence as the most perturbed molecular mechanisms. These perturbations correlated with histopathological observations. Only weak perturbations were observed for pMRTP. In conclusion, a correlative evaluation of classical histopathology together with gene expression-based computational network models may facilitate a systems toxicology-based risk assessment, as shown for a pMRTP.

Noninvasive assessment of the risk of tobacco abuse in oral mucosa using fluorescence spectroscopy: a clinical approach

Tobacco abuse and alcoholism cause cancer, emphysema, and heart disease, which contribute to high death rates, globally. Society pays a significant cost for these habits whose first demonstration in many cases is in the oral cavity. Oral cavity disorders are highly curable if a screening procedure is available to diagnose them in the earliest stages. The aim of the study is to identify the severity of tobacco abuse, in oral cavity, as reflected by the emission from endogenous fluorophores and the chromophore hemoglobin. A group who had no tobacco habits and another with a history of tobacco abuse were included in this study. To compare the results with a pathological condition, a group of leukoplakia patients were also included. Emission from porphyrin and the spectral filtering modulation effect of hemoglobin were collected from different sites. Multivariate analysis strengthened the spectral features with a sensitivity of 60% to 100% and a specificity of 76% to 100% for the discrimination. Total hemoglobin and porphyrin levels of habitués and leukoplakia groups were comparable, indicating the alarming situation about the risk of tobacco abuse. Results prove that fluorescence spectroscopy along with multivariate analysis is an effective noninvasive tool for the early diagnosis of pathological changes due to tobacco abuse.

Glutathione peroxidase-1 as a novel therapeutic target for COPD

Oxidative stress plays a role in a variety of diseases but it is even more pertinent in chronic obstructive pulmonary disease (COPD) given the increased oxidant burden in smokers. The increased oxidant burden results from the fact that cigarette smoke contains over 4700 different chemical compounds and more than 10(15) oxidants/free radicals per puff. Other factors, such as air pollutants, infections, and occupational dusts that may exacerbate COPD, also have the potential to produce oxidative stress. These oxidants give rise to Reactive Oxygen Species (ROS) that are generated enzymatically by inflammatory and epithelial cells within the lung as part of an inflammatory immune response towards a pathogen or irritant. Thus, while ROS are necessary for host defence against invading pathogens, increased levels of ROS have been implicated in initiating inflammatory responses in the lungs through the activation of transcriptional factors, signal transduction pathways, chromatin remodelling and gene expression of pro-inflammatory mediators. However, the normal lung has developed defences to ROS-mediated damage, which include antioxidant enzymes such as superoxide dismutase, catalase, and glutathione peroxidase. In this review we consider the therapeutic potential of the antioxidant enzyme glutathione peroxidase-1 for the treatment of cigarette smoke-induced lung inflammation and damage.

Simvastatin inhibits smoke-induced airway epithelial injury: implications for COPD therapy

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death. The statin drugs may have therapeutic potential in respiratory diseases such as COPD, but whether they prevent bronchial epithelial injury is unknown. We hypothesised that simvastatin attenuates acute tobacco smoke-induced neutrophilic lung inflammation and airway epithelial injury. Spontaneously hypertensive rats were given simvastatin (20 mg·kg(-1) i.p.) daily for either 7 days prior to tobacco smoke exposure and during 3 days of smoke exposure, or only during tobacco smoke exposure. Pretreatment with simvastatin prior to and continued throughout smoke exposure reduced the total influx of leukocytes, neutrophils and macrophages into the lung and airways. Simvastatin attenuated tobacco smoke-induced cellular infiltration into lung parenchymal and airway subepithelial and interstitial spaces. 1 week of simvastatin pretreatment almost completely prevented smoke-induced denudation of the airway epithelial layer, while simvastatin given only concurrently with the smoke exposure had no effect. Simvastatin may be a novel adjunctive therapy for smoke-induced lung diseases, such as COPD. Given the need for statin pretreatment there may be a critical process of conditioning that is necessary for statins' anti-inflammatory effects. Future work is needed to elucidate the mechanisms of this statin protective effect.

Adverse effects of wood smoke PM(2.5) exposure on macrophage functions

Epidemiological studies have shown a correlation between chronic biomass smoke exposure and increased respiratory infection. Pulmonary macrophages are instrumental in both the innate and the adaptive immune responses to respiratory infection. In the present study, in vitro systems were utilized where alveolar macrophages (AM) and bone marrow-derived macrophages (BMdM) were exposed to concentrated wood smoke-derived particulate matter (WS-PM) and mice were exposed in vivo to either concentrated WS-PM or inhaled WS. In vivo studies demonstrated that WS-exposed mice inoculated with Streptococcus pneumoniae had a higher bacterial load 24 h post-exposure, and corresponding AM were found to have decreased lymphocyte activation activity. Additionally, while classic markers of inflammation (cellular infiltration, total protein, neutrophils) were not affected, there were changes in pulmonary macrophages populations, including significant decreases in macrophages expressing markers of activation in WS-exposed mice. The lymphocyte activation activity of WS-PM-exposed AM was significantly suppressed, but the phagocytic activity appeared unchanged. In an effort to determine a pathway for WS-induced suppression, RelB activation, assessed by nuclear translocation, was observed in AM exposed to either inhaled WS or instilled WS-PM. Finally, an analysis of WS-PM fractions determined the presence of 4-5 polycyclic aromatic hydrocarbons (PAHs), and preliminary work suggests a potential role for these PAHs to alter macrophage functions. These studies show a decreased ability of WS-exposed pulmonary macrophages to effectively mount a defense against infection, the effect lasts at least a week post-exposure, and appears to be mediated via RelB activation.

Tobacco smoke induced COPD/emphysema in the animal model-are we all on the same page?

Chronic Obstructive Pulmonary Disease (COPD) is one of the foremost causes of death worldwide. It is primarily caused by tobacco smoke, making it an easily preventable disease, but facilitated by genetic α-1 antitrypsin deficiency. In addition to active smokers, health problems also occur in people involuntarily exposed to second hand smoke (SHS). Currently, the relationship between SHS and COPD is not well established. Knowledge of pathogenic mechanisms is limited, thereby halting the advancement of new treatments for this socially and economically detrimental disease. Here, we attempt to summarize tobacco smoke studies undertaken in animal models, applying both mainstream (direct, nose only) and side stream (indirect, whole body) smoke exposures. This overview of 155 studies compares cellular and molecular mechanisms as well as proteolytic, inflammatory, and vasoreactive responses underlying COPD development. This is a difficult task, as listing of exposure parameters is limited for most experiments. We show that both mainstream and SHS studies largely present similar inflammatory cell populations dominated by macrophages as well as elevated chemokine/cytokine levels, such as TNF-α. Additionally, SHS, like mainstream smoke, has been shown to cause vascular remodeling and neutrophil elastase-mediated proteolytic matrix breakdown with failure to repair. Disease mechanisms and therapeutic interventions appear to coincide in both exposure scenarios. One of the more widely applied interventions, the anti-oxidant therapy, is successful for both mainstream and SHS. The comparison of direct with indirect smoke exposure studies in this review emphasizes that, even though there are many overlapping pathways, it is not conclusive that SHS is using exactly the same mechanisms as direct smoke in COPD pathogenesis, but should be considered a preventable health risk. Some characteristics and therapeutic alternatives uniquely exist in SHS-related COPD.

Is intrinsic aerobic exercise capacity a determinant of COPD susceptibility?

Chronic obstructive pulmonary disease is a leading cause of morbidity and mortality, which is most commonly associated with smoking or exposure to environmental pollutants. Unfortunately, there is an inadequate understanding of the molecular and physiological determinants governing one's susceptibility for developing COPD. Here, we describe a novel hypothesis: Individuals with intrinsically low aerobic exercise capacity are more likely to develop COPD after exposure to key risk factors. The hypothesis is based on observations that aerobic exercise capacity is tightly associated with mortality across many complex diseases. The premise is supported by recent studies demonstrating that smokers who exercise regularly are less likely to develop or be hospitalized for COPD. Herein, we describe the evolutionary and molecular basis for this hypothesis and how it is a natural extension of previous theories explaining COPD susceptibility.

Strategies to decrease ongoing oxidant burden in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a leading cause of mortality and morbidity globally, and its development is mainly associated with tobacco/biomass smoke-induced oxidative stress. Hence, targeting systemic and local oxidative stress with agents that can balance the antioxidant/redox system can be expected to be useful in the treatment of COPD. Preclinical and clinical trials have revealed that antioxidants/redox modulators can detoxify free radicals and oxidants, control expression of redox and glutathione biosynthesis genes, chromatin remodeling and inflammatory gene expression; and are especially useful in preventing COPD exacerbations. In this review, various novel approaches and problems associated with these approaches in COPD are reviewed.

Prior exercise training alleviates the lung inflammation induced by subsequent exposure to environmental cigarette smoke

AIM

Environmental cigarette smoke (CS) contains many compounds that are harmful to the respiratory system and lead to chronic lung inflammation and other lung diseases. Exercise training is known to confer protection against diseases with chronic inflammation by reducing inflammatory response in human or experimental animals. In this study, we investigated the preventive effect of exercise training against lung inflammation induced by environmental CS.

METHODS AND RESULTS

In this study, two groups of mice received air exposure with (the exercise group) or without (the control group) exercise training for 8 weeks and another two groups received air exposure for the first 4 weeks and CS exposure for the following 4 weeks with (the exercise+CS group) or without (the CS group) exercise training for 8 weeks. As compared with lung tissues of control and exercise groups, those of the CS group showed significantly increased bronchoalveolar-capillary permeability, inflammatory cell infiltration, epithelial thickening, expression of proliferating cell nuclear antigen, mucin 2, cytokines, chemokines, adhesion molecules and activation of NF-κB. These CS-induced pathophysiologic consequences were largely prevented in the exercise + CS group.

CONCLUSION

Collectively, prior exercise training may protect against lung inflammation induced by environmental CS in mice by attenuating the activation of NF-κB and the production of inflammatory mediators.

Improvement of enzymatic stability and intestinal permeability of deuterohemin-peptide conjugates by specific multi-site N-methylation

The deuterohemin-peptide conjugate, DhHP-6 (Dh-β-AHTVEK-NH(2)), is a microperoxidase mimetic, which has demonstrated substantial benefits in vivo as a scavenger of reactive oxygen species (ROS). In this study, specific multi-site N-methylated derivatives of DhHP-6 were designed and synthesized to improve metabolic stability and intestinal absorption, which are important factors for oral delivery of therapeutic peptides and proteins. The DhHP-6 derivatives were tested for (1) scavenging potential of hydrogen peroxide (H(2)O(2)); (2) permeability across Caco-2 cell monolayers and everted gut sacs; and (3) enzymatic stability in serum and intestinal homogenate. The results indicated that the activities of the DhHP-6 derivatives were not influenced by N-methylation, and that tri-N-methylation of DhHP-6 could significantly increase intestinal flux, resulting in a two- to threefold higher apparent permeability coefficient. In addition, molecules with N-methylation at selected sites (e.g., Glu residue) showed high resistance against proteolytic degradation in both diluted serum and intestinal preparation, with 50- to 140-fold higher half-life values. These findings suggest that the DhHP-6 derivatives with appropriate N-methylation could retain activity levels equivalent to that of the parent peptide, while showing enhanced intestinal permeability and stability against enzymatic degradation. The tri-N-methylated peptide Dh-β-AH(Me)T(Me)V(Me)EK-NH(2) derived from this study may be developed as a promising candidate for oral administration.

Use of a soluble epoxide hydrolase inhibitor in smoke-induced chronic obstructive pulmonary disease

Tobacco smoke-induced chronic obstructive pulmonary disease (COPD) is a prolonged inflammatory condition of the lungs characterized by progressive and largely irreversible airflow limitation attributable to a number of pathologic mechanisms, including bronchitis, bronchiolitis, emphysema, mucus plugging, pulmonary hypertension, and small-airway obstruction. Soluble epoxide hydrolase inhibitors (sEHIs) demonstrated anti-inflammatory properties in a rat model after acute exposure to tobacco smoke. We compared the efficacy of sEHI t-TUCB (trans-4-{4-[3-(4-trifluoromethoxy-phenyl)-ureido]-cyclohexyloxy}-benzoic acid) and the phosphodiesterase-4 (PDE4) inhibitor Rolipram (Biomol International, Enzo Life Sciences, Farmingdale, NY) to reduce lung injury and inflammation after subacute exposure to tobacco smoke over a period of 4 weeks. Pulmonary physiology, bronchoalveolar lavage, cytokine production, and histopathology were analyzed to determine the efficacy of sEHI and Rolipram to ameliorate tobacco smoke-induced inflammation and injury in the spontaneously hypertensive rat. Both t-TUCB and Rolipram inhibited neutrophil elevation in bronchoalveolar lavage. sEHI t-TUCB suppressed IFN-γ, while improving lung function by reducing tobacco smoke-induced total respiratory resistance and tissue damping (small-airway and peripheral tissue resistance). Increases in tobacco smoke-induced alveolar airspace size were attenuated by t-TUCB. Rolipram inhibited the production of airway mucus. Both t-TUCB and Rolipram inhibited vascular remodeling-related growth factor. These findings suggest that sEHI t-TUCB has therapeutic potential for treating COPD by improving lung function and attenuating the lung inflammation and emphysematous changes caused by tobacco smoke. To the best of our knowledge, this is the first report to demonstrate that sEHI exerts significant protective effects after repeated, subacute tobacco smoke-induced lung injury in a rat model of COPD.

Antioxidant pharmacological therapies for COPD

Increased oxidative stress occurs in the lungs and systemically in COPD, which plays a role in many of the pathogenic mechanisms in COPD. Hence, targeting local lung and systemic oxidative stress with agents that modulate the antioxidants/redox system or boost endogenous antioxidants would be a useful therapeutic approach in COPD. Thiol antioxidants (N-acetyl-l-cysteine [NAC] and N-acystelyn, carbocysteine, erdosteine, and fudosteine) have been used to increase lung thiol content. Modulation of cigarette smoke (CS) induced oxidative stress and its consequent cellular changes have also been reported to be effected by synthetic molecules, such as spin traps (α-phenyl-N-tert-butyl nitrone), catalytic antioxidants (superoxide dismutase [ECSOD] mimetics), porphyrins, and lipid peroxidation and protein carbonylation blockers/inhibitors (edaravone and lazaroids/tirilazad). Preclinical and clinical trials have shown that these antioxidants can reduce oxidative stress, affect redox and glutathione biosynthesis genes, and proinflammatory gene expression. In this review the approaches to enhance lung antioxidants in COPD and the potential beneficial effects of antioxidant therapy on the course of the disease are discussed.

Pharmacological antioxidant strategies as therapeutic interventions for COPD

Cigarette/tobacco smoke/biomass fuel-induced oxidative and aldehyde/carbonyl stress are intimately associated with the progression and exacerbation of chronic obstructive pulmonary disease (COPD). Therefore, targeting systemic and local oxidative stress with antioxidants/redox modulating agents, or boosting the endogenous levels of antioxidants are likely to have beneficial effects in the treatment/management of COPD. Various antioxidant agents, such as thiol molecules (glutathione and mucolytic drugs, such as N-acetyl-L-cysteine and N-acystelyn, erdosteine, fudosteine, ergothioneine, and carbocysteine), have been reported to modulate various cellular and biochemical aspects of COPD. These antioxidants have been found to scavenge and detoxify free radicals and oxidants, regulate of glutathione biosynthesis, control nuclear factor-kappaB (NF-kappaB) activation, and hence inhibiting inflammatory gene expression. Synthetic molecules, such as specific spin traps like α-phenyl-N-tert-butyl nitrone, a catalytic antioxidant (ECSOD mimetic), porphyrins (AEOL 10150 and AEOL 10113), and a superoxide dismutase mimetic M40419, iNOS and myeloperoxidase inhibitors, lipid peroxidation inhibitors/blockers edaravone, and lazaroids/tirilazad have also been shown to have beneficial effects by inhibiting cigarette smoke-induced inflammatory responses and other carbonyl/oxidative stress-induced cellular alterations. A variety of oxidants, free radicals, and carbonyls/aldehydes are implicated in the pathogenesis of COPD, it is therefore, possible that therapeutic administration or supplementation of multiple antioxidants and/or boosting the endogenous levels of antioxidants will be beneficial in the treatment of COPD. This review discusses various novel pharmacological approaches adopted to enhance lung antioxidant levels, and various emerging beneficial and/or prophylactic effects of antioxidant therapeutics in halting or intervening the progression of COPD. This article is part of a Special Issue entitled: Antioxidants and Antioxidant Treatment in Disease.

Patterns of cytokine release and evolution of remote organs from proximal femur fracture in COPD rats

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is at increased risk for developing osteoporosis (OP) with subsequent proximal femur fracture. The presence of COPD is suggested to be a strong risk factor for proximal femur fracture or hip fracture. However, what happen behind it is not clearly understood.

OBJECTIVE

To investigate the pattern of cytokine (TNF-a, IL-6, and IL-10) releases in pulmonary and hepatic in rats with COPD suffering from proximal femur fracture, and its possible adverse effect on pulmonary and hepatic.

METHODS AND SUBJECTIVE

This paper has two parts. In the first part, we describe the procedure of COPD model in detail. In the second part, we study the influences of fracture on the COPD rats. 5 months WISTAR rats with 37 weeks cigarette smoking exposure (CS group) were dynamically determined for pulmonary function, inflammatory response in bronchoalveolar lavage fluid (BALF), histological changes in pulmonary in the first part. When the COPD model is proved to be successful, we begin the second part. COPD rats were euthanized at 2, 24, 48, 72, and 96h after proximal femur fracture (fracture group) or anaesthesia (control group). Cytokines (TNF-a, IL-6, and IL-10) and myeloperoxidase activity of pulmonary and hepatic (MPO) were measured with enzyme-liked immunosorbent assay technique. Permeability changes of the lung were assessed via bronchoalveolar lavage, and those of the liver via assessment of oedema formation. Tissues were further examined microscopically.

RESULTS

The current sidestream cigarette smoke induced rat COPD model has been proved an adequate animal model with several advantages as assessed by dynamically monitored lung mechanics and pathological changes for 37 weeks. In the second part, TNF-a, IL-6, and IL-10 levels of pulmonary tissue were significantly increased after proximal femur fracture compared to control rats. TNF-a, and IL-6 levels in pulmonary peaked at 2h, 24h in fracture group, whereas IL-10 level peaked at 24h and 96h. Pulmonary myeloperoxidase activity, permeability and histological score in fracture group were remarkably elevated, and peaked at 24h. In addition to TNF-a, all above parameters did not return to normal through our study. Hepatic in COPD rats showed notable increase of cytokines (TNF-a, IL-6, and IL-10), myeloperoxidase activity, histological score, and permeability in fracture group compared to control rats, and severity of these changes were much lower than in pulmonary. Apart from TNF-a, the peak of these parameters was at 24h after fracture. Changes of cytokines, MPO activity, permeability and histological score in pulmonary and hepatic in control rat were little changed.

CONCLUSION

COPD rats produced a remarkably increase of inflammatory response (TNF-a, IL-6, IL-10) in lung (liver) after proximal femur fracture, which lead to lung (liver) injury, as evidence by changes of MPO, permeability, and histological scores in local organs.

The anti-inflammatory effects of soluble epoxide hydrolase inhibitors are independent of leukocyte recruitment

Excess leukocyte recruitment to the lung plays a central role in the development or exacerbation of several lung inflammatory diseases including chronic obstructive pulmonary disease. Epoxyeicosatrienoic acids (EETs) are cytochrome P-450 metabolites of arachidonic acid reported to have multiple biological functions, including blocking of leukocyte recruitment to inflamed endothelium in cell culture through reduction of adhesion molecule expression. Inhibition of the EET regulatory enzyme, soluble epoxide hydrolase (sEH) also has been reported to have anti-inflammatory effects in vivo including reduced leukocyte recruitment to the lung. We tested the hypothesis that the in vivo anti-inflammatory effects of sEH inhibitors act through the same mechanisms as the in vitro anti-inflammatory effects of EETs in a rat model of acute inflammation following exposure to tobacco smoke. Contrary to previously published data, we found that sEH inhibition did not reduce tobacco smoke-induced leukocyte recruitment to the lung. Furthermore, sEH inhibition did not reduce tobacco smoke-induced adhesion molecule expression in the lung vasculature. Similarly, concentrations of EETs greater than or equal to their reported effective dose did not reduce TNFα induced expression of the adhesion molecules. These results suggest that the anti-inflammatory effects of sEH inhibitors are independent of leukocyte recruitment and EETs do not reduce the adhesion molecules responsible for leukocyte recruitment in vitro. This demonstrates that the widely held belief that sEH inhibition prevents leukocyte recruitment via EET prevention of adhesion molecule expression is not consistently reproducible.

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

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

Preclinical animal models of asthma and chronic obstructive pulmonary disease

Animal models of disease serve a vital function in the search for novel therapeutic approaches. While these systems cannot replicate human disease, they can be used to mimic and investigate mechanisms believed to be central to disease pathogenesis. In this review, we discuss the most relevant and commonly used animal models for asthma and chronic obstructive pulmonary disease (COPD); specifically, models developed for the mouse, rat and guinea pig. Allergens, such as ovalbumin, can be used to induce an IgE-dependent response characterized by early- and late-phase bronchoconstriction, inflammation and airway hyper-responsiveness similar to what occurs in asthmatics. Similarly, elastase and cigarette smoke can be used to replicate steroid-insensitive and progressive inflammation, which leads to lung pathologies that are observed in COPD patients. We also discuss how these models are developing in new ways to more closely reflect the clinical disease. Unfortunately, these models have limitations due to differences in genetics, anatomy and physiology among the species, many of which we have highlighted; however, understanding these differences, careful characterization of these models and parallel in vitro or ex vivo studies using human and relevant animal tissues will overcome some of these issues. In spite of these limitations, as long as studies are designed and interpreted appropriately, in vivo models will continue to be vital for furthering our understanding of disease pathogenesis and for developing new therapies.

Hypoxia inducible factor 1alpha signaling in fractionated radiation-induced lung injury: role of oxidative stress and tissue hypoxia

To investigate the relationship of HIF1alpha signaling to oxidative stress, tissue hypoxia, angiogenesis and inflammation, female Fischer 344 rats were irradiated to the right hemithorax with a fractionated dose of 40 Gy (8 Gy x 5 days). The lung tissues were harvested before and at 4, 6, 10, 14, 18, 22 and 26 weeks after irradiation for serial studies of biological markers, including markers for hypoxia (HIF1alpha, pimonidazole and CA IX), oxidative stress (8-OHdG), and angiogenesis/capillary proliferation (VEGF/CD 105), as well as macrophage activation (ED-1) and cell signaling/fibrosis (NFkappaB, TGFbeta1), using immunohistochemistry and Western blot analysis. HIF1alpha staining could be observed as early as 4 weeks postirradiation and was significantly increased with time after irradiation. Importantly, HIF1alpha levels paralleled oxidative stress (8-OHdG), tissue hypoxia (pimonidazole and CA IX), and macrophage accumulation consistent with inflammatory response. Moreover, changes in HIF1alpha expression identified by immunohistochemistry assay parallel the changes in TGFbeta1, VEGF, NFkappaB and CD 105 levels in irradiated lungs. These results support the notion that oxidative stress and tissue hypoxia might serve as triggering signals for HIF1alpha activity in irradiated lungs, relating to radiation-induced inflammation, angiogenesis and fibrosis.

Characterisation of the proximal airway squamous metaplasia induced by chronic tobacco smoke exposure in spontaneously hypertensive rats

Background

Continuous exposure to tobacco smoke (TS) is a key cause of chronic obstructive pulmonary disease (COPD), a complex multifactorial disease that is difficult to model in rodents. The spontaneously hypertensive (SH) rat exhibits several COPD-associated co-morbidities such as hypertension and increased coagulation. We have investigated whether SH rats are a more appropriate animal paradigm of COPD.

Methods

SH rats were exposed to TS for 6 hours/day, 3 days/week for 14 weeks, and the lung tissues examined by immunohistochemistry.

Results

TS induced a CK13-positive squamous metaplasia in proximal airways, which also stained for Ki67 and p63. We hypothesise that this lesion arises by basal cell proliferation, which differentiates to a squamous cell phenotype. Differences in staining profiles for the functional markers CC10 and surfactant D, but not phospho-p38, indicated loss of ability to function appropriately as secretory cells. Within the parenchyma, there were also differences in the staining profiles for CC10 and surfactant D, indicating a possible attempt to compensate for losses in proximal airways. In human COPD sections, areas of CK13-positive squamous metaplasia showed sporadic p63 staining, suggesting that unlike the rat, this is not a basal cell-driven lesion.

Conclusion

This study demonstrates that although proximal airway metaplasia in rat and human are both CK13+ and therefore squamous, they potentially arise by different mechanisms.

Development and characterization of a rat model of chronic obstructive pulmonary disease (COPD) induced by sidestream cigarette smoke

Cigarette smoke (CS) induced chronic obstructive pulmonary disease (COPD) has been emerging as a great health problem in China. However, lack of appropriate animal model slows down the progress in understanding pathogenesis of the disease. The aim of current study is to establish and evaluate a more adequate rat model of COPD. Study was performed with rats exposed to sidestream cigarette smoke 2h/d and 7d/wk for 2, 4, 6, 8, 10, 12, 24 and 36 wk in a CS chamber (carbon monoxide concentration was 231+/-11ppm). The lung function was determined by using the forced oscillation technique. Pathologic changes were determined by using histological analyses and mucin measurement. Following 36-wk exposure, airway resistance (Raw) and respiratory system elastance (Ers) in CS group rats was elevated by 28.5% and 37.5%, respectively. Up to 4.1-, 2.3- and 1.4-fold increase in the number of neutrophils, macrophages and lymphocytes was observed in the BALF of CS rats. Using quantitative histomorphology techniques, it was found that mean linear intercept (MLI) and mean alveolar airspace (MAA) of CS rats increased by 44.8% and 43.7%, respectively, indicating the occurrence of emphysema. The characteristics of chronic bronchitis including hyperplasia of bronchial epithelial cells, hypersecretion of mucus and development of peribronchial fibrosis were also found in rat lungs. CS group rats showed 43% body weight gain reduction. To conclude, a more adequate sidestream cigarette smoke rat COPD model was established, which will be beneficial for understanding the pathogenesis of the disease and for evaluation of drug effectiveness.

Smoking enhances risk for new external genital warts in men

Repeat episodes of HPV-related external genital warts reflect recurring or new infections. No study before has been sufficiently powered to delineate how tobacco use, prior history of EGWs and HIV infection affect the risk for new EGWs. Behavioral, laboratory and examination data for 2,835 Multicenter AIDS Cohort Study participants examined at 21,519 semi-annual visits were evaluated. Fourteen percent (391/2835) of men reported or were diagnosed with EGWs at 3% (675/21,519) of study visits. Multivariate analyses showed smoking, prior episodes of EGWs, HIV infection and CD4+ T-lymphocyte count among the infected, each differentially influenced the risk for new EGWs.

Antioxidant therapeutic advances in COPD

Chronic obstructive pulmonary disease (COPD) is associated with a high incidence of morbidity and mortality. Cigarette smoke-induced oxidative stress is intimately associated with the progression and exacerbation of COPD and therefore targeting oxidative stress with antioxidants or boosting the endogenous levels of antioxidants is likely to have beneficial outcome in the treatment of COPD. Among the various antioxidants tried so far, thiol antioxidants and mucolytic agents, such as glutathione, N-acetyl-L-cysteine, N-acystelyn, erdosteine, fudosteine and carbocysteine; Nrf2 activators; and dietary polyphenols (curcumin, resveratrol, and green tea catechins/quercetin) have been reported to increase intracellular thiol status along with induction of GSH biosynthesis. Such an elevation in the thiol status in turn leads to detoxification of free radicals and oxidants as well as inhibition of ongoing inflammatory responses. In addition, specific spin traps, such as alpha-phenyl-N-tert-butyl nitrone, a catalytic antioxidant (ECSOD mimetic), porphyrins (AEOL 10150 and AEOL 10113), and a SOD mimetic M40419 have also been reported to inhibit cigarette smoke-induced inflammatory responses in vivo in the lung. Since a variety of oxidants, free radicals and aldehydes are implicated in the pathogenesis of COPD, it is possible that therapeutic administration of multiple antioxidants and mucolytics will be effective in management of COPD. However, a successful outcome will critically depend upon the choice of antioxidant therapy for a particular clinical phenotype of COPD, whose pathophysiology should be first properly understood. This article will review the various approaches adopted to enhance lung antioxidant levels, antioxidant therapeutic advances and recent past clinical trials of antioxidant compounds in COPD.