The pharmokinetic limitations of antioxidant treatment 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.

Mitochondria in Focus: From Function to Therapeutic Strategies in Chronic Lung Diseases

Mitochondria are essential organelles for cell metabolism, growth, and function. Mitochondria in lung cells have important roles in regulating surfactant production, mucociliary function, mucus secretion, senescence, immunologic defense, and regeneration. Disruption in mitochondrial physiology can be the central point in several pathophysiologic pathways of chronic lung diseases such as chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, and asthma. In this review, we summarize how mitochondria morphology, dynamics, redox signaling, mitophagy, and interaction with the endoplasmic reticulum are involved in chronic lung diseases and highlight strategies focused on mitochondrial therapy (mito-therapy) that could be tested as a potential therapeutic target for lung diseases.

Targeting c-Src Reverses Accelerated GPX-1 mRNA Decay in Chronic Obstructive Pulmonary Disease Airway Epithelial Cells

Enhanced expression of the cellular antioxidant glutathione peroxidase (GPX)-1 prevents cigarette smoke-induced lung inflammation and tissue destruction. Subjects with chronic obstructive pulmonary disease (COPD), however, have decreased airway GPX-1 levels, rendering them more susceptible to disease onset and progression. The mechanisms that downregulate GPX-1 in the airway epithelium in COPD remain unknown. To ascertain these factors, analyses were conducted using human airway epithelial cells isolated from healthy subjects and human subjects with COPD and lung tissue from control and cigarette smoke-exposed A/J mice. Tyrosine phosphorylation modifies GPX-1 expression and cigarette smoke activates the tyrosine kinase c-Src. Therefore, studies were conducted to evaluate the role of c-Src on GPX-1 levels in COPD. These studies identified accelerated GPX-1 mRNA decay in COPD airway epithelial cells. Targeting the tyrosine kinase c-Src with siRNA inhibited GPX-1 mRNA degradation and restored GPX-1 protein levels in human airway epithelial cells. In contrast, silencing the tyrosine kinase c-Abl, or the transcriptional activator Nrf2, had no effect on GPX-1 mRNA stability. The chemical inhibitors for c-Src (saracatinib and dasanitib) restored GPX-1 mRNA levels and GPX-1 activity in COPD airway cells in vitro. Similarly, saracatinib prevented the loss of lung Gpx-1 expression in response to chronic smoke exposure in vivo. Thus, this study establishes that the decreased GPX-1 expression that occurs in COPD lungs is at least partially due to accelerated mRNA decay. Furthermore, these findings show that targeting c-Src represents a potential therapeutic approach to augment GPX-1 responses and counter smoke-induced lung disease.

Mechanisms of ultrafine particle-induced respiratory health effects

Particulate matter (PM) is the principal component of air pollution. PM includes a range of particle sizes, such as coarse, fine, and ultrafine particles. Particles that are <100 nm in diameter are defined as ultrafine particles (UFPs). UFPs are found to a large extent in urban air as both singlet and aggregated particles. UFPs are classified into two major categories based on their source. Typically, UFPs are incidentally generated in the environment, often as byproducts of fossil fuel combustion, condensation of semivolatile substances or industrial emissions, whereas nanoparticles are manufactured through controlled engineering processes. The primary exposure mechanism of PM is inhalation. Inhalation of PM exacerbates respiratory symptoms in patients with chronic airway diseases, but the mechanisms underlying this response remain unclear. This review offers insights into the mechanisms by which particles, including UFPs, influence airway inflammation and discusses several mechanisms that may explain the relationship between particulate air pollutants and human health, particularly respiratory health. Understanding the mechanisms of PM-mediated lung injury will enhance efforts to protect at-risk individuals from the harmful health effects of air pollutants.

Comparison of oxidant/antioxidant balance in COPD and non-COPD smokers

BACKGROUND/AIM

Oxidative stress plays an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD). Smoking is the leading source of oxidants in lungs. However, it is currently unknown why some individuals are more resistant to the detrimental effects of smoking and do not develop COPD. The aim in this study is to measure and compare the oxidant/antioxidant balance between in non-COPD individuals who smoke and COPD patients who smoke.

MATERIALS AND METHODS

Included in the study were 137 patients with COPD and 102 healthy individuals. Participants were divided into groups as COPD patients (former and current smokers), non-COPD individuals who smoke and non-smokers healthy persons. In the following stage, the total antioxidant status (TAS), total oxidant status (TOS) and oxidative stress index (OSI) levels were measured in serum for all participants.

RESULTS

In the current-smoker COPD group, the level of oxidant status were significantly higher than the former-smoker COPD group (p < 0.001). Similarly, oxidant levels were significantly high in current-smoker healthy group than never smoker healthy group. According to these results TOS was associated with especially smoking status rather than COPD. Antioxidant status were similar between former-smoker COPD group and current-smoker COPD group. The antioxidant levels were found significantly low in current-smoker COPD patients, compared to the current-smoker non-COPD individuals (p = 0.007). Nevertheless, no significant difference was found in OSI levels between two groups. Briefly, high TOS and OSI values were correlated with only smoking, independently from COPD.

CONCLUSION

It was concluded that there are complex pathogenetic mechanisms, including genetic and individual variations other than oxidant/antioxidant balance, involved in the development of smoking-related COPD. TOS and OSI values are not predictive parameters for the development of COPD, but high level of TAS in non-COPD smokers is promising for future studies.

Evaluation of the oxidant and antioxidant balance in the pathogenesis of chronic obstructive pulmonary disease

Chronic Obstructive Pulmonary Disease (COPD) is one of the most common chronic diseases and a major cause of morbility and mortality. An imbalance between oxidants and antioxidants (oxidative stress) has been proposed as a critical event in the pathogenesis of COPD. The increased oxidative stress in patients with COPD is the result of exogenous oxidants namely pollutants and cigarette smoke as well as endogenous oxidant production during inflammation. The aim of the present study was to clarify the hypothesis about the presence of an imbalance between oxidants and the antioxidant defences associated to COPD. In this study, we evaluated a biomarker of oxidative stress (malondialdehyde, a lipid peroxidation derived product) and non-enzymatic antioxidants (vitamin C and the sulphydryl groups) in COPD patients and healthy controls. The marker of oxidative stress was found to be significantly (p<0,001) higher in COPD patients when compared with the control group. No age dependent changes in the plasma levels of lipid peroxidation products were found. COPD patients had a significant (p<0,001) decrease in antioxidant status compared with control group. Our results show that oxidative stress is an important pathophysiologic change in COPD.

Anti-inflammatory role of the cAMP effectors Epac and PKA: implications in chronic obstructive pulmonary disease

Cigarette smoke-induced release of pro-inflammatory cytokines including interleukin-8 (IL-8) from inflammatory as well as structural cells in the airways, including airway smooth muscle (ASM) cells, may contribute to the development of chronic obstructive pulmonary disease (COPD). Despite the wide use of pharmacological treatment aimed at increasing intracellular levels of the endogenous suppressor cyclic AMP (cAMP), little is known about its exact mechanism of action. We report here that next to the β(2)-agonist fenoterol, direct and specific activation of either exchange protein directly activated by cAMP (Epac) or protein kinase A (PKA) reduced cigarette smoke extract (CSE)-induced IL-8 mRNA expression and protein release by human ASM cells. CSE-induced IκBα-degradation and p65 nuclear translocation, processes that were primarily reversed by Epac activation. Further, CSE increased extracellular signal-regulated kinase (ERK) phosphorylation, which was selectively reduced by PKA activation. CSE decreased Epac1 expression, but did not affect Epac2 and PKA expression. Importantly, Epac1 expression was also reduced in lung tissue from COPD patients. In conclusion, Epac and PKA decrease CSE-induced IL-8 release by human ASM cells via inhibition of NF-κB and ERK, respectively, pointing at these cAMP effectors as potential targets for anti-inflammatory therapy in COPD. However, cigarette smoke exposure may reduce anti-inflammatory effects of cAMP elevating agents via down-regulation of Epac1.

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

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