The pharmokinetic limitations of antioxidant treatment for COPD

Abstract

COPD is one of the leading causes of death worldwide and the age-adjusted mortality for this disease has risen significantly over the past thirty years. Current pharmacological treatments do not effectively address the inflammatory and apoptotic mechanisms that are critical in the development of this disease. Thus, despite therapy, patients typically experience a continued deterioration of their clinical status. Markers of oxidative stress are increased in the lungs of COPD patients and epidemiologic and animal studies indicate that antioxidants can protect the lungs from the damaging effects of cigarette smoke. To date, however, clinical trials of antioxidants for COPD have yielded disappointing results. This review discusses the pharmokinetic factors that limit the use of exogenous antioxidants as a treatment for this disease. In addition, it addresses strategies to overcome these limitations so that the beneficial properties of antioxidants can be translated into effective therapies for COPD patients. KeywordsAntioxidants; Chronic Obstructive Pulmonary Disease; Emphysema; Inflammation; Cigarette Smoke; Bioavailability Limitations of current pharmacotherapeutic agents in the treatment of COPDChronic Obstructive pulmonary disease (COPD) affects 13.5 million Americans(1) and now ranks as the fourth leading cause of death nationwide. While great strides have been made in the treatment of cardiovascular diseases, the age-adjusted mortality for chronic obstructive pulmonary disease (COPD) has actually risen 71% over the past thirty years(2). Indeed, estimates predict that COPD will be the third leading cause of death and the fifth leading cause of disability worldwide by the year 2020(3,4). In order to improve these trends in the future, it is imperative that pharmacologic agents be developed that can halt or reverse the pathophysiologic changes that occur in this disease. Current guidelines for COPD management advocate the use of inhaled β 2 -agonists, inhaled anticholinergics and inhaled corticosteroids for symptomatic management(5). Long acting bronchodilators including the anti-cholinergic tiotropium, given once daily, and the β 2 -agonists salmeterol and formoterol given twice daily all improve lung function, quality of life and reduce the time to first exacerbation when compared to placebo(6-8). Likewise, several clinical trials have shown that inhaled steroids significantly reduce the rate of exacerbations in COPD(9,10). Importantly, a recent study demonstrated that combination therapy with salmeterol and fluticasone proprionate reduced Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply...

Anti-Inflammatory Role of the cAMP Effectors Epac and PKA: Implications in Chronic Obstructive Pulmonary Disease

“…Our data point at post-translational modification of Epac1, as Epac1 mRNA levels in COPD patients did not differ from the mRNA levels in the control subjects. Lung damage and chronic inflammation by cigarette smoke-induced oxidative stress caused irreversible alterations in protein structure [41] . Such alterations might play a role in the down-regulation of Epac1 protein in COPD patients.…”

Mechanisms of ultrafine particle-induced respiratory health effects

“…During asthma exacerbation in humans, the levels of serum thioredoxin (TRX1) increase and are inversely correlated with airflow 48 . Cigarette smoke induces increased oxidant burden and causes irreversible changes to the protective antioxidant effects in the airways 48 .…”

“…During asthma exacerbation in humans, the levels of serum thioredoxin (TRX1) increase and are inversely correlated with airflow 48 . Cigarette smoke induces increased oxidant burden and causes irreversible changes to the protective antioxidant effects in the airways 48 . The smoke-derived oxidants damage airway epithelial cells, inducing direct injury to membrane lipids, proteins, carbohydrates, and DNA, leading to chronic inflammation 48 .…”

“…Cigarette smoke induces increased oxidant burden and causes irreversible changes to the protective antioxidant effects in the airways 48 . The smoke-derived oxidants damage airway epithelial cells, inducing direct injury to membrane lipids, proteins, carbohydrates, and DNA, leading to chronic inflammation 48 . Cigarette smoking delivers and generates oxidative stress within the lungs 49 .…”

Particulate Air Pollutants and Respiratory Diseases

“…Cigarette smoke can induce increased oxidant burden and cause irreversible changes to the antioxidant protective effects in the airways (van Der Troorn, et al, 2007). The smokederived oxidants damage airway epithelial cells inducing direct injury to membrane lipids, proteins, carbohydrates, and DNA, leading to chronic inflammation (Foronjy, et al, 2008). Cigarette smoking delivers and generates oxidative stress within the lungs (Lin & Thoma, 2010) These imbalances of oxidant burden and antioxidant capacity have been implicated as important contributing factors in the pathogenesis of COPD (Lin & Thoma, 2010) However, smoking also causes the depletion of antioxidants, which further contributes to oxidative tissue damage (Lin & Thoma, 2010) The downregulation of antioxidant pathways has also been associated with acute exacerbations of COPD (Lin & Thoma, 2010).…”