Decreased leukocyte deformability after acute cigarette smoking in humans

Cigarette smoking increases plasma levels of IL-6 and TNF-α

Background and objective: Cigarette smoking is a leading cause of a wide range of critical health problems such as cancers, especially those who are related to the respiratory system. Although studies are continuing on the smoking-related inflammatory responses, limited reports are there to explore how such responses can be affected by the smoking intensity. Therefore, the current communication aimed to shed light on how smoking and smoking intensity can affect some inflammatory and anti-inflammatory biomarkers. Methods: A total of 159 subjects (108 smokers and 51 non-smokers) were enrolled in this cross-sectional study. Their sociodemographic, smoking intensity and blood samples were obtained and processed using approved methodologies. The blood plasma samples were used to quantify interleukin 6 (IL-6), IL-10, tumor necrosis factor-alpha (TNF-α), C-reactive protein, D-dimer, and ferritin by using ELISA. The gained data was then analyzed using GraphPad Prism software to assess the variations. Results: The results showed that IL-6 and TNF-α are elevated markedly (p<0.001) in smoker subjects when compared with non-smoker ones (IL-6: 2.58±0.98 vs. 1.858±0.6256 pg/ml, TNF-α: 28.38±7.162 vs. 22.64±7.257). However, no significant differences were observed in other biomarkers comparing the groups, as well as no significant association was evidenced based on smoking intensity among smokers. Conclusions: The findings might point to a relationship between smoking and the elevation of IL-6 and TNF-α levels in a cigarette dose-dependent manner.

The relationship between smoking intensity and subclinical cardiovascular injury: The Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND AND AIMS

Modern tobacco regulatory science requires an understanding of which biomarkers of cardiovascular injury are most sensitive to cigarette smoking exposure.

METHODS

We studied self-reported current smokers from the Multi-Ethnic Study of Atherosclerosis. Smoking intensity was defined by number of cigarettes/day and urinary cotinine levels. Subclinical cardiovascular injury was assessed using markers of inflammation [high-sensitivity C-reactive protein (hsCRP), interleukin 6 & 2 (IL-2 & IL-6), tumor necrosis factor alpha (TNF-α)], thrombosis (fibrinogen, D-dimer, homocysteine), myocardial injury (troponin T; TnT), endothelial damage (albumin: creatinine ratio), and vascular function [aortic & carotid distensibility, flow-mediated dilation (FMD)]. Biomarkers were modeled as absolute and percent change using multivariable-adjusted linear regression models adjusted for cardiovascular risk factors and smoking duration.

RESULTS

Among 843 current smokers, mean age was 58 (9) years, 53% were men, 39% were African American, mean number of cigarettes per day was 13 (10), and median smoking duration was 39 (15) years. Cigarette count was significantly associated with higher hsCRP, IL-6 and fibrinogen (β coefficients: 0.013, 0.011, 0.60 respectively), while ln-transformed cotinine was associated with the same biomarkers (β coefficients: 0.12, 0.04, 5.3 respectively) and inversely associated with aortic distensibility (β coefficient: -0.13). There was a limited association between smoking intensity and homocysteine, D-dimer, and albumin:creatinine ratio in partially adjusted models only, while there was no association with IL-2, TNF-α, carotid distensibility, FMD, or TnT in any model. In percent change analyses, relationships were strongest with hsCRP.

CONCLUSIONS

Smoking intensity was associated with early biomarkers of CVD, particularly, markers of systemic inflammation. Of these, hsCRP may be the most sensitive.

Cigarette smoking and airway wall thickness on CT scan in a multi-ethnic cohort: the MESA Lung Study

BACKGROUND

Autopsy studies show that smoking contributes to airway wall hyperplasia and narrowing of the airway lumen. Studies of smoking and airway measures on computed tomography (CT) scan are limited to case-control studies of measures that combine airway lumen and wall thickness.

OBJECTIVES

We hypothesized that cumulative cigarette smoking would be associated with increased airway wall thickness in a large, population-based cohort.

METHODS

The Multi-Ethnic Study of Atherosclerosis enrolled participants age 45-84 years from the general population. Smoking history was assessed via standardized questionnaire items; current smoking was confirmed in half the cohort with cotinine. Airway lumen and wall thickness were measured in two dimensions in posterior basal segmental bronchi on cardiac-gated CT scans. Analyses were adjusted for age, gender, genetic ancestry, education, height, weight, asthma history, particulate matter, scanner type, and scanner current.

RESULTS

Half of the 7898 participants had smoked and 14% were current smokers. Pack-years of smoking were associated with thicker airway walls (mean increase 0.002 mm per ten pack-years [95% CI: 0.00002, 0.004] p = 0.03). Current smoking was associated with narrower airway lumens (mean decrease -0.11 mm [95% CI: -0.2, -0.02] p = 0.02). There was no evidence that either association was modified by genetic ancestry, and findings persisted among participants without clinical disease.

CONCLUSIONS

Long-term cigarette smoking was associated with subclinical increases in wall thickness of sub-segmental airways whereas current smoking was associated with narrower airway lumen diameters. Smoking may contribute to airway wall thickening prior to the development of overt chronic obstructive pulmonary disease.

Effect of copper-hydroquinone complex on oxidative stress-related parameters in human erythrocytes (in vitro)

The effect of in vitro exposure of human erythrocytes to micromolar concentrations of hydroquinone and copper simultaneously on oxidative status-related biochemical parameters was studied. Hydroquinone is a component of cigarette smoke and serum copper level is increased in smokers. Copper forms a complex with hydroquinone and enhances its auto-oxidation to benzoquinone which covalently binds to sulfhydryl group containing compounds like reduced glutathione. In this study, copper increased H(2)O(2) production by hydroquinone. Hydroquinone either alone or in the presence of copper produced a decrease of reduced glutathione level without altering methemoglobin concentration and erythrocyte lipid peroxidation. Catalase inhibition by sodium azide depleted reduced glutathione level further. Copper-hydroquinone complex mediated glutathione depletion in the catalase containing RBC was not decreased by antioxidant, butylated hydroxytoluene. From the known facts and above findings, it is suggested that depletion of reduced glutathione by hydroquinone in the presence of copper in catalase active RBC may be due to the formation of 1, 4 benzoquinone adduct of reduced glutathione and to some extent due to binding of copper to the thiol group of reduced glutathione rather than conversion to oxidized glutathione via reactive oxygen species. Depletion of reduced glutathione by N-ethylmaleimide pretreatment followed by copper-hydroquinone treatment had no effect on methemoglobin level or lipid peroxidation. Furthermore, copper-hydroquinone complex did not increase erythrocyte susceptibility to oxidative stress. This suggests hydroquinone in the presence of copper does not contribute to erythrocyte membrane lipid peroxidation seen in smokers. Criteria for ideal antioxidant supplementation in smokers were suggested.

Radical generation and alterations of erythrocyte integrity as bioindicators of diagnostic or prognostic value in COPD?

Chronic obstructive pulmonary disease (COPD) has recently been viewed as an inflammation-dependent systemic disease. Oxidative modifications in the pulmonary microenvironment can result in a number of functional changes in pulmonary tissue as well as in the blood. Studies have been carried out to detect whether oxidatively modified molecules or cells could be considered possible markers of the disease. We hypothesize here that new insights into COPD could come from enzymes involved in deliberate radical generation (i.e., Nox and NOS family enzymes) as well as from alterations of erythrocyte integrity and function, which could become bioindicators of diagnostic or prognostic value in the near future.

Oxidative stress, inflammation, and pulmonary function assessment in rats exposed to laboratory-generated pollutant mixtures

Oxidative stress may mediate adverse health effects of many inhaled pollutants. Cardiopulmonary responses of Sprague-Dawley rats to inhalation of whole or filtered gasoline engine exhaust (GEE, FGEE); simulated downwind coal emission atmospheres (SDCAs) from two types of coal, each tested at two concentrations; and two concentrations of re-aerosolized paved road dust (RD) were evaluated. In situ chemiluminescence and thiobarbituric acid-reactive substances (TBARS) were used to evaluate oxidative reactions in the lungs, heart, and liver immediately following exposures. Pulmonary inflammatory responses were measured by bronchoalveolar lavage (BAL) cell counts. Respiratory function parameters during exposure were measured by plethysmography. Only GEE significantly enhanced in situ chemiluminescence (all three organs), but only exposure to the high RD concentration increased TBARS (hearts only). There was a weak trend toward increased macrophages recovered in lavage fluid from both SDCAs, and macrophages were significantly elevated by both FGEE and the lower concentration of RD. Respiratory function effects were small, though the effects of the Central Appalachian low-sulfur SDCA on enhanced pause and the effects of the Powder River Basin SCDA on tidal volume were significant. The discordance between the oxidative stress indicators may relate to the use of a single time point in the context of dynamic changes in compensatory mechanisms. These results further suggest that inflammatory responses measured by BAL cellularity may not always correlate with oxidative stress. Overall, the toxicological effects from exposure to these pollutant mixtures were subtle, but the results show differences in the effects of atmospheres having different physical/chemical characteristics.

Aspects on pathophysiological mechanisms in COPD

Chronic obstructive pulmonary disease (COPD) is a condition which is characterized by irreversible airway obstruction due to narrowing of small airways, bronchiolitis, and destruction of the lung parenchyma, emphysema. It is the fourth most common cause of mortality in the world and is expected to be the third most common cause of death by 2020. The main cause of COPD is smoking but other exposures may be of importance. Exposure leads to airway inflammation in which a variety of cells are involved. Besides neutrophil granulocytes, macrophages and lymphocytes, airway epithelial cells are also of particular importance in the inflammatory process and in the development of emphysema. Cell trafficking orchestrated by chemokines and other chamoattractants, the proteinase-antiproteinase system, oxidative stress and airway remodelling are central processes associated with the development of COPD. Recently systemic effects of COPD have attracted attention and the importance of systemic inflammation has been recognized. This seems to have direct therapeutic implications as treatment with inhaled glucocorticosteroids has been shown to influence mortality. The increasing body of knowledge regarding the inflammatory mechanism in COPD will most likely have implications for future therapy and new drugs, specifically aimed at interaction with the inflammatory processes, are currently being developed.

Inflammation, edema, and peripheral blood changes in lung-compromised rats after instillation with combustion-derived and manufactured nanoparticles

Increased exposure to pollution has been implicated in cardiovascular malfunction, and although studies show a relationship between PM10 and mortality, the exact biological causes are unclear. This study investigated how compromised lungs respond to instillation of nanoparticles, and the links between exposure to nanoparticles and the subsequent effects on the blood. Instillation of diesel exhaust particles and Cabosil caused significant permeability and inflammatory changes in both bleomycin-treated and control lungs, as shown by increased lung surface protein and lung:body weight ratio. This was true in edematous and maximally repairing lungs, but without significant hematological alterations. Plasma viscosity, a renowned marker for cardiovascular disease, correlated strongly statistically with free cell numbers, type I cell marker rT140, and lung acellular protein. These correlations are a new and novel insight into the mechanisms linking air pollution to cardiovascular mortality.

Oxidative stress and airway inflammation in severe exacerbations of COPD

BACKGROUND

A study was undertaken to assess both oxidative stress and inflammation in the lungs of patients with chronic obstructive pulmonary disease (COPD) during severe and very severe exacerbations compared with those with stable COPD, healthy smokers, and non-smokers. Two sites within the lungs were compared: the large airways (in sputum) and the peripheral airways (by bronchoalveolar lavage (BAL)).

METHODS

BAL fluid cell numbers and levels of tumour necrosis factor (TNFalpha) and interleukin (IL)-8 were measured as markers of airway inflammation and glutathione (GSH) levels as a marker of antioxidant status. Nuclear translocation of the pro-inflammatory transcription factors nuclear factor-kappaB (NF-kappaB) and activator protein 1 (AP-1) were also measured by electromobility shift assay in BAL fluid leucocytes and lung biopsy samples.

RESULTS

Influx of inflammatory cells into the peripheral airways during exacerbations of COPD was confirmed. Increased IL-8 levels were detected in BAL fluid from patients with stable COPD compared with non-smokers and healthy smokers, with no further increase during exacerbations. In contrast, IL-8 levels in the large airways increased during exacerbations. GSH levels were increased in the BAL fluid of smokers (444%) and patients with stable COPD (235%) compared with non-smokers and were reduced during exacerbations (severe 89.2%; very severe 52.3% compared with stable COPD). NF-kappaB DNA binding in BAL leucocytes was decreased in healthy smokers compared with non-smokers (41.3%, n = 9, p<0.001) but did not differ in COPD patients, whereas AP-1 DNA binding was significantly decreased during exacerbations of COPD.

CONCLUSION

There is evidence of increased oxidative stress in the airways of patients with COPD that is increased further in severe and very severe exacerbations of the disease. This is associated with increased neutrophil influx and IL-8 levels during exacerbations.

[Oxidative stress in bronchopulmonary disease: contribution of N-acetylcysteine (NAC)]

Oxidative stress is a frequent mechanism involved in the pathogenesis of bronchopulmonary disease. The cause can be exogenous, in particular related to to atmospheric pollution and tobacco smoke, or endogenous, related to mobilization of inflammatory cells (macrophages and polymorphonuclear neutrophils). In this general review, we present work demonstrating this oxidative stress and activation of inflammatory cells. We discuss the effect of oxidative stress on the bronchial tree and the need to maintain an adequate balance between oxidants and anti-oxidants. This reviews focuses on experimental studies proving the anti-oxidant effect of NAC on glutathione synthesis and on different pharmacological models. We then discuss human trials, initially experimental then in different bronchopulmonary pathologies related to oxidative stress. Acetaminophen intoxication and pulmonary fibrosis are models for use of NAC. Recent work on COPD appears to show a decrease in exacerbations, improvement in symptoms and quality-of-life, and perhaps a reduction in the alteration of ventilatory function.

Acute effects of cigarette smoke on inflammation and oxidative stress: a review

Compared with the effects of chronic smoke exposure on lung function and airway inflammation, there are few data on the acute effects of smoking. A review of the literature identified 123 studies investigating the acute effects of cigarette smoking on inflammation and oxidative stress in human, animal, and in vitro models. An acute smoking model is a relatively easy and sensitive method of investigating the specific effects of cigarette smoke on oxidative stress and inflammation. Acute smoke exposure can result in tissue damage, as suggested by increased products of lipid peroxidation and degradation products of extracellular matrix proteins. Acute cigarette smoke has a suppressive effect on the number of eosinophils and several inflammatory cytokines, possibly due to the anti-inflammatory effect of carbon monoxide. An acute smoking model can supplement other ways of studying the effects of smoking and is an as yet underinvestigated method for intervention studies in smoking related diseases.

The role of oxidative stress in chronic obstructive pulmonary disease

Tobacco smoke is the number one risk factor for chronic obstructive pulmonary disease (COPD) and contains a high concentration of oxidants. The lung has a high concentration of antioxidants and antioxidant enzymes; however, COPD patients show evidence of increased oxidative stress suggesting that endogenous antioxidants may be insufficient to prevent oxidative damage from cigarette smoke. The consequences of increased oxidative stress in the lung include increased transcription of inflammatory genes, increased protease activity, and increased mucus secretion. Oxidative stress is often associated with impaired skeletal muscle function and may be one of the causes of glucocorticoid resistance. While current pharmacologic approaches to the treatment of chronic obstructive pulmonary disease do not commonly include antioxidants, preclinical studies involving animal models suggest that antioxidant superoxide dismutase mimetics offer a potential new therapeutic approach to the prevention and treatment of chronic obstructive pulmonary disease.

Neutrophil capture by selectins on endothelial cells exposed to cigarette smoke

We used a novel perfusion system to expose cultured human umbilical vein endothelial cells (HUVEC) to water-soluble components of cigarette smoke and study subsequent adhesion of flowing neutrophils. Neutrophils did not bind to HUVEC immediately after it had been exposed to cigarette smoke, but many adhered 90-150 min after exposure. The effect was reduced if the exposed medium was made serum-free, but this reduction was partially reversed if low density lipoprotein was added. Treatment of smoke-exposed HUVEC with antibodies against E-selectin or P-selectin reduced adhesion by approximately 50% or 75%, respectively; a combination of both antibodies essentially abolished adhesion. Enzyme-linked immunosorbent assay confirmed that exposure to smoke caused HUVEC to upregulate surface expression of E- and P-selectin. Thus, water-soluble constituent(s) of cigarette smoke cause efficient selectin-mediated capture of flowing neutrophils. This pro-inflammatory response may contribute to pathology associated with smoking, especially in tissues remote from the lung.

Oxidative stress and lung inflammation in airways disease

Oxidative stress results from an oxidant/antioxidant imbalance in favour of oxidants. A large number of studies have demonstrated that increased oxidative burden occurs in airways diseases, shown by increased marks of oxidative stress in the airspaces and systemically in these patients. There is now substantial evidence that oxidative stress plays an important role in the injurious and inflammatory responses in airways diseases such as asthma and chronic obstructive pulmonary disease (COPD). In addition to these proinflammatory mechanisms resulting from oxidative stress, protective mechanisms such as the upregulation of protective antioxidant genes also occur. At present, effective antioxidant therapy that has good bioavailability and potency is not available. Such drugs are being developed and should in the future allow the hypothesis that oxidative stress is a fundamental factor in the inflammation, which occurs in these airways diseases to be tested.

Effects of cigarette smoke in mice with different levels of alpha(1)-proteinase inhibitor and sensitivity to oxidants

The role of strain difference in the response to cigarette smoke was investigated in mice. Mice of the strains DBA/2 and C57BL/6J responded to acute cigarette smoke with a decrease of the antioxidant defenses of their bronchoalveolar lavage (BAL) fluids. On the other hand, under these conditions ICR mice increased their BAL antioxidant defenses. Mice of these three strains were then exposed to cigarette smoke (three cigarettes/d, 5 d/wk) for 7 mo. Lung elastin content was significantly decreased in C57BL/6J and DBA/2 but not in ICR mice. Also, emphysema, assessed morphometrically using three methods, was present in C57BL/6J and DBA/2 but not in ICR mice. In an additional study pallid mice, with a severe serum alpha(1)-proteinase inhibitor (alpha(1)-PI) deficiency and that develop spontaneous emphysema, were exposed to cigarette smoke for 4 mo. This resulted in an acceleration of the development of the spontaneous emphysema assessed with morphometrical and biochemical (lung elastin content) methods. All these results indicate that sensitivity to the effects of cigarette smoke is strain-dependent and cigarette smoke accelerates the effects of alpha(1)-PI deficiency.

Protective effects of n-acetylcysteine on lung injury and red blood cell modification induced by carrageenan in the rat

Oxidative stress has been suggested as a potential mechanism in the pathogenesis of lung inflammation. The pharmacological profile of n-acetylcysteine (NAC), a free radical scavenger, was evaluated in an experimental model of lung injury (carrageenan-induced pleurisy). Injection of carrageenan into the pleural cavity of rats elicited an acute inflammatory response characterized by fluid accumulation in the pleural cavity that contained many neutrophils (PMNs), an infiltration of PMNs in lung tissues and subsequent lipid peroxidation, and increased production of nitrite/nitrate, tumor necrosis factor alpha, and interleukin 1beta. All parameters of inflammation were attenuated by NAC treatment. Furthermore, carrageenan induced an up-regulation of the adhesion molecules ICAM-1 and P-selectin, as well as nitrotyrosine and poly (ADP-ribose) synthetase (PARS), as determined by immunohistochemical analysis of lung tissues. The degree of staining for the ICAM-1, P-selectin, nitrotyrosine, and PARS was reduced by NAC. In vivo NAC treatment significantly reduced peroxynitrite formation as measured by the oxidation of the fluorescent dihydrorhodamine-123, prevented the appearance of DNA damage, an decrease in mitochondrial respiration, and partially restored the cellular level of NAD+ in ex vivo macrophages harvested from the pleural cavity of rats subjected to carrageenan-induced pleurisy. A significant alteration in the morphology of red blood cells was observed 24 h after carrageenan administration. NAC treatment has the ability to significantly diminish the red blood cell alteration. Our results clearly demonstrate that NAC treatment exerts a protective effect and clearly indicate that NAC offers a novel therapeutic approach for the management of lung injury where radicals have been postulated to play a role.

Is oxidative stress central to the pathogenesis of chronic obstructive pulmonary disease?

There is now considerable evidence for an increased oxidant burden in patients with chronic obstructive pulmonary disease (COPD). Oxidative stress is a critical feature in the pathogenesis of COPD, since it results in inactivation of antiproteinases, airspace epithelial injury, MUCUS HYPERSECRETION, increased influx of neutrophils into the lungs, transcription factor activation and gene expression of pro-inflammatory mediators. Antioxidants should therefore not only protect against the direct injurious effects of oxidants, but also may fundamentally alter the inflammatory events which have a central role in the pathogenesis of COPD.

Increased exhalation of hydrogen peroxide in healthy subjects following cigarette consumption

CONTEXT

Increased hydrogen peroxide has been described in the expired breath condensate (H2O2-E) of several lung conditions, such as acute respiratory distress syndrome, chronic obstructive pulmonary disease and asthma. This technique has been advocated as being a simple method for documenting airway inflammation.

OBJECTIVE

To evaluate H2O2-E in healthy cigarette smokers, and to determine the acute effects of the consumption of one cigarette on H2O2-E levels.

TYPE OF STUDY

Prospective, controlled trial.

SETTING

A pulmonary function laboratory in a University Hospital.

PARTICIPANTS

Two groups of healthy volunteers: individuals who had never smoked (NS; n=10; 4 men; age = 30.6 +/- 6.2 years) and current cigarette smokers (S; n=12; 7 men; age = 38.7 +/- 9.8). None of the volunteers had respiratory symptoms and all showed normal spirometric tests.

INTERVENTION

Expired air was collected from all volunteers through a face mask and a plastic collecting system leading into a flask with dry ice and pure ethanol. Samples from the group S were collected twice, before and half an hour after the combustion of one cigarette.

MAIN MEASUREMENTS

Expired hydrogen peroxide using the Gallati and Pracht method.

RESULTS

The S and NS groups showed comparable levels of H2O2-E at basal conditions [NS = 0.74 microM (DP 0.24) vs. S = 0.75 microM (DP 0.31)]. The smokers showed a significant increase in H2O2-E levels half an hour after the consumption of only one cigarette [0.75 microM (DP 0.31) vs. 0. 95 microM (DP 0.22)].

CONCLUSION

The present results are consistent with the concept that smokers increase oxidative stress with elevated production of reactive oxygen species, contributing to the development of smoking-related disorders.

Exacerbations of COPD: environmental mechanisms

Air pollution as a trigger for exacerbations of COPD has been recognized for > 50 years, and has led to the development of air quality standards in many countries that substantially decreased the levels of air pollutants derived from the burning of fossil fuels, such as black smoke and sulfur dioxide. However, the recent dramatic increase in motor vehicle traffic has produced a relative increase in the levels of newer pollutants, such as ozone and fine-particulate air pollution < 10 microm in diameter. Numerous epidemiologic studies have shown associations between the levels of these air pollutants and adverse health effects, such as exacerbations of airways diseases and even deaths from respiratory and cardiovascular causes. Elucidation of the mechanism of the harmful effects of these pollutants should allow improved risk assessment for patients with airways diseases who are be susceptible to the effects of these air pollutants.

Oxidants/antioxidants and COPD

Oxidative stress results from an oxidant/antioxidant imbalance, an excess of oxidants and/or a depletion of antioxidants. Oxidative stress is thought to play an important role in the pathogenesis of a number of lung diseases, not only through direct injurious effects, but by involvement in the molecular mechanisms that control lung inflammation. A number of studies have shown an increased oxidant burden and consequently increased markers of oxidative stress in the airspaces, breath, blood, and urine in smokers and in patients with COPD. The presence of oxidative stress has important consequences for the pathogenesis of COPD. These include oxidative inactivation of antiproteinases, airspace epithelial injury, increased sequestration of neutrophils in the pulmonary microvasculature, and gene expression of proinflammatory mediators. With regard to the latter, oxidative stress has a role in enhancing the inflammation that occurs in smokers and patients with COPD, through the activation of redox-sensitive transcriptions factors such as nuclear factor-kappaB and activator protein-1, which regulate the genes for proinflammatory mediators and protective antioxidant gene expression. The sources of the increased oxidative stress in patients with COPD are derived from the increased burden of oxidants present in cigarette smoke, or from the increased amounts of reactive oxygen species released from leukocytes, both in the airspaces and in the blood. Antioxidant depletion or deficiency in antioxidants may contribute to oxidative stress. The development of airflow limitation is related to dietary deficiency of antioxidants, and hence dietary supplementation may be a beneficial therapeutic intervention in this condition. Antioxidants that have good bioavailability or molecules that have antioxidant enzyme activity may be therapies that not only protect against the direct injurious effects of oxidants, but may fundamentally alter the inflammatory events that play an important part in the pathogenesis of COPD.

Smoking and chronic obstructive pulmonary disease

Smoking is overwhelmingly the major cause of chronic bronchitis and emphysema worldwide. Additional risk factors for developing COPD are presented, along with the variables that govern cigarette smoke deposition in the lung. Major paradigms for the pathogenesis of COPD, including the protease-antiprotease and oxidant-antioxidant theories are described, and evidence for impaired reparative mechanisms in the causation of emphysema is noted. A description of the natural history of declining lung function in smokers and in the susceptible subset of smokers that ultimately develop smoking-induced COPD is accompanied by a discussion of the effects of smoking cessation on preservation of lung health. The disordered ventilation and gas-exchange physiology in the cigarette smoke-damaged lung is explained on the basis of the observed morphological changes.

Oxidants and antioxidants as therapeutic targets in chronic obstructive pulmonary disease

There is now increasing evidence that an oxidant/antioxidant imbalance, in favor of oxidants, occurs in chronic obstructive pulmonary disease (COPD). Evidence is also accumulating that oxidative stress is a critical event in the pathogenesis of this condition. A large number of studies have demonstrated an increased oxidant burden and consequently increased markers of oxidative stress in the airspaces, breath, blood, and urine of smokers and of patients with COPD. There are several events related to oxidative stress, which are important in the pathogenesis of COPD. These include oxidative inactivation of antiproteinases, airspace epithelial injury, increased sequestration of neutrophils in the pulmonary microvasculature, and gene expression of proinflammatory mediators. Oxidative processes have a fundamental role in the inflammation of smokers and patients with COPD, through redox-sensitive transcription factors such as NF-kappaB and AP-1, which regulate the genes for proinflammatory mediators and protective mechanisms, such as antioxidant gene expression. In addition to the oxidative stress produced by cigarette smoking, dietary deficiency in antioxidants is related to the development of airflow limitation, and hence dietary supplementation may be a beneficial therapeutic intervention in this condition. The use of antioxidants with good bioavailability or molecules that have antioxidant enzyme activity may be treatments that not only protect against the direct injurious effects of oxidants, but may fundamentally alter the inflammatory events that are thought to play an important part in the pathogenesis of COPD. MacNee W, Rahman I. Oxidants and antioxidants as therapeutic targets in chronic obstructive pulmonary disease.

A single high dose of vitamin C counteracts the acute negative effect on microcirculation induced by smoking a cigarette

Cigarette smoking is associated with marked acute changes in microcirculation including reduced blood flow. We tested the hypothesis that the reduced blood flow velocity is due to the imbalance between prooxidants and antioxidants that occurs as a consequence of smoking and that it can be reduced by an antioxidant. The effect of smoking a single cigarette on nail-fold microcirculation was analyzed in 24 healthy subjects with varying smoking habits. Vital capillary microscopy was used and the blood cell flow velocity in the capillaries was evaluated before and 1-30 min after smoking. Smoking induced a marked decrease in microcirculatory blood flow in 23 of the 24 subjects (40-50% decrease 1-5 min after smoking). This change was reduced by more than 50% in the same subjects after intake of 2 g of vitamin C 2 h before smoking (P < 0.0001 by ANOVA test) with smokers responding similarly to nonsmokers in these experiments. Intake of 1 g of vitamin C had no significant effect on the smoking-induced changes in most of the subjects tested (n = 11). Pretreatment with aspirin had little or no effect on the response to smoking (n = 9). Our results show that treatment with a single high dose of vitamin C can reduce and in some individuals even completely abolish the negative acute effect on microcirculation induced by smoking a single cigarette. This effect of vitamin C is not likely to be mediated by the cyclooxygenase system.

The role of cigarette smoke in the pathogenesis of asthma and as a trigger for acute symptoms

Although it has been long believed that cigarette smoke is injurious to the lower respiratory tract, the exact early mechanisms and early events responsible for this injury remain unclear. Maternal smoking, particularly in utero, is clearly associated with an increased risk for the later development of childhood atopy and asthma. Smoking is known to increase the inflammatory burden of the lower respiratory tract through a number of related but separate mechanisms. These include the recruitment of increased numbers of inflammatory cells, alteration in cell subtypes, enhancement of some cellular functions, and proinflammatory mediator release. In addition, cigarette smoking in vitro and in animal models appears to promote neurogenic inflammation, increase oxidative stress and lead to the elevation of cysteinyl leukotrienes, all of which could potentially lead to an amplification of the airway inflammation already present in asthmatics. Greater and more consistent effort must be given to encourage the young asthmatic not to smoke. In addition, greater effort must be spent on smoking cessation, especially in pregnant women and young asthmatics.

Quitting smoking raises whole blood glutathione

Cigarette smoke contains numerous oxygen free radicals that may be important in smoking-related disease pathogenesis. These free radicals may overwhelm antioxidant defenses and produce a condition of oxidative stress that can result in damage to DNA and other cellular components. This study investigated whether or not indications of harmful oxidative stress decline following smoking cessation. Changes in whole blood glutathione (GSH), an index of oxidative stress level, were determined for 30 cigarette smokers who participated in an experimental smoking-cessation program. Measurements were taken during ad lib smoking and 3 weeks after smoking cessation. In 22 individuals who were continuously abstinent for 3 weeks, GSH levels rose significantly following smoking cessation, from 5.0 to 6.1 mumol/g Hb (p < 0.001). Individuals with the lowest GSH levels during ad lib smoking showed the greatest increases following cessation. Results suggest that oxidative stress and free-radical damage diminish soon after smoking cessation. Thus, some significant health benefits may appear rapidly when people quit smoking.

Role of oxidants/antioxidants in smoking-induced lung diseases

An imbalance between oxidants and antioxidants has been considered in the pathogenesis of smoking-induced lung diseases, such as chronic obstructive pulmonary disease (COPD), particularly emphysema. Recent evidence indicates that increased neutrophil sequestration and activation occurs in the pulmonary microvasculature in smokers and in patients with COPD, with the potential to release reactive oxygen species (ROS). ROS generated by airspace phagocytes or inhaled directly from the environment also increase the oxidant burden and may contribute to the epithelial damage. Although much research has focused on the protease/antiprotease theory of the pathogenesis of emphysema, less attention has been paid to the role of ROS in this condition. The injurious effects of the increased oxidant burden in smokers and in patients with COPD are opposed by the lung antioxidant defences. Hence, determining the mechanisms regulating the antioxidant responses is critical to our understanding of the role of oxidants in the pathogenesis of smoking-induced lung disease and to devising future strategies for antioxidant therapy. In this article we have reviewed the evidence for the presence of an oxidant/antioxidant imbalance in smoking-induced lung disease and its relevance to therapy in these conditions.

Vitamin C prevents cigarette smoke-induced leukocyte aggregation and adhesion to endothelium in vivo

A common feature of cigarette-smoke (CS)-associated diseases such as atherosclerosis and pulmonary emphysema is the activation, aggregation, and adhesion of leukocytes to micro- and macrovascular endothelium. A previous study, using a skinfold chamber model for intravital fluorescence microscopy in awake hamsters, has shown that exposure of hamsters to the smoke generated by one research cigarette elicits the adhesion of fluorescently labeled leukocytes to the endothelium of arterioles and small venules. By the combined use of intravital microscopy and scanning electron microscopy, we now demonstrate in the same animal model that (i) CS-induced leukocyte adhesion is not confined to the microcirculation, but that leukocytes also adhere singly and in clusters to the aortic endothelium; (ii) CS induces the formation in the bloodstream of aggregates between leukocytes and platelets; and (iii) CS-induced leukocyte adhesion to micro- and macrovascular endothelium and leukocyte-platelet aggregate formation are almost entirely prevented by dietary or intravenous pretreatment with the water-soluble antioxidant vitamin C (venules, 21.4 +/- 11.0 vs. 149.6 +/- 38.7 leukocytes per mm2, P < 0.01; arterioles, 8.5 +/- 4.2 vs. 54.3 +/- 21.6 leukocytes per mm2, P < 0.01; aortas, 0.8 +/- 0.4 vs. 12.4 +/- 5.6 leukocytes per mm2, P < 0.01; means +/- SD of n = 7 animals, 15 min after CS exposure). No inhibitory effect was observed by pretreatment of the animals with the lipid-soluble antioxidants vitamin E or probucol. The protective effects of vitamin C on CS-induced leukocyte adhesion and aggregation were seen at vitamin C plasma levels (55.6 +/- 22.2 microM, n = 7) that can easily be reached in humans by dietary means or supplementation, suggesting that vitamin C effectively contributes to protection from CS-associated cardiovascular and pulmonary diseases in humans.