A pilot study of all-trans-retinoic acid for the treatment of human emphysema

Strategies to modulate immune responses: a new frontier for gene therapy

The success of gene therapy strategies to cure disease relies on the control of unwanted immune responses to transgene products, genetically modified cells and/or to the vector. Effective treatment of an established immune response is much harder to achieve than prevention of a response before it has had a chance to develop. However, preventive strategies are not always effective in avoiding immune responses, thus the use of drugs to induce immunosuppression (IS) is required. The growing discovery of novel drugs provides a conceptual shift from using generalized, moderately intensive immunosuppressive regimens towards a refined approach to attain the optimal balance of naive cells, effector cells, memory cells, and regulatory cells, harnessing the natural tolerance mechanisms of the body. We review several strategies based on transient IS coupled with gene therapy for sustained immune tolerance induction to the therapeutic transgene.

INHALATION ADMINISTRATION OF ALL-TRANS-RETINOIC ACID FOR TREATMENT OF ELASTASE-INDUCED PULMONARY EMPHYSEMA IN FISCHER 344 RATS

A past study demonstrated that all-trans-retinoic acid (ATRA) treatment by intraperitoneal injection in a rat model of elastase-induced emphysema caused tissue regeneration as evidenced by a decrease in alveolar size and lung volume and an increase in alveolar number. We postulated that treatment with this retinoid by nose-only inhalation exposure would be a more efficient means of targeting damaged lung tissue. Emphysema was induced in male Fischer 344 rats by intratracheal instillation of pancreatic elastase (0.5 IU/g body weight). Four weeks after elastase instillation, animals were treated once daily, 4 days/week, for 3 weeks by exposing them nose-only to aerosolized ATRA (target concentration-time of 3000 or 15,000 mg-min/m3) or by injecting them intraperitoneally with ATRA in cottonseed oil (0.5 or 2.5 mg/kg). Based on estimates of particle deposition in the respiratory tract, inhalation doses were chosen to be consistent with injected doses. Lungs were fixed by inflation with formalin (constant pressure for 6 hours followed by >48 hours of immersion) and were embedded in paraffin. Sections were evaluated by histopathology and stereology. Inhalation exposure to ATRA at both aerosol concentrations caused significant elevations of ATRA in the lung, whereas only the high-dose injection treatment was associated with an elevation of lung ATRA. The mean ATRA concentration from lungs of rats in the high-dose inhalation exposure groups as measured by liquid chromatography--mass spectrometry was approximately 12-fold greater than that of high-dose injection-treated rats. Elastase instillation caused increased lung volumes, irregular alveolar air space enlargement, and fragmentation and attenuation of alveolar septa. Neither inhaled nor injected ATRA reduced the enlarged lung volumes associated with this emphysema model. Stereology demonstrated that alveolar air space enlargement in ATRA-treated rats was similar to that in sham-treated emphysematous animals. Thus, while inhalation treatment caused greater levels of the drug in lung tissue in comparison to that of injection-treated animals, treatment with ATRA by either route of administration did not cause a reversal of lung tissue damage in this model of elastase-induced emphysema.

Interactions of alpha1-proteinase inhibitor with small ligands of therapeutic potential: binding with retinoic acid

Human alpha(1)-proteinase inhibitor (alpha(1)-PI), also known as alpha(1)-antitrypsin, is the most abundant plasma serine protease inhibitor (serpin). It is best recognized for inhibition of neutrophil elastase. The alpha(1)-PI interactions with non-protease ligands were investigated mainly in regards to those molecules that may block the aggregation of alpha(1)-PI Z mutant. The objective of this study was to evaluate the potential of alpha(1)-PI to bind small non-peptide ligands of pharmaceutical interest that may attain additional properties to currently available alpha(1)-PI therapeutic preparations. Among putative ligands of bio-medical interest examined in this study, all-trans retinoic acid (RA) was selected due to its recently proposed roles in the lungs, and as an efficient optical probe. The results of this study, including absorption spectroscopy data, fluorescence quenching and the protein-induced chirality of the visible circular dichroism strongly suggest that alpha(1)-PI does bind RA in vitro to non-covalent complexes of up to two moles of RA per one mole of the protein. To our knowledge, this is the first report that provides experimental evidence of the alpha(1)-PI potential towards bi-functional drugs via a combination with RA, or potentially other molecules of pharmaceutical interest, that ultimately, may enhance currently available alpha(1)-PI therapies.

Tissue regeneration as next-generation therapy for COPD--potential applications

COPD is a major cause of chronic morbidity and mortality worldwide, and there is a need to develop more effective therapeutic strategies to replace specialized treatment such as lung transplantation. Recent studies suggest that recognition of apoptotic lung epithelial or endothelial cells may result in growth factors to stimulate cell replacement, and defects in these processes may contribute to the pathogenesis of COPD. Furthermore, recent animal and human studies have revealed that tissue-specific stem cells and bone marrow-derived cells contribute to lung tissue regeneration and protection, and thus administration of exogenous stem/progenitor cells or humoral factors responsible for activation of endogenous stem/progenitor cells may be a potent next-generation therapy for COPD.

Reconstruction of emphysematous lung tissue using slowly released basic fibroblast growth factor from gelatin microspheres

Basic fibroblast growth factor (bFGF) has a variety of activities including regeneration and neovascularization. This study was an attempt to reconstruct emphysematous lung tissue employing slow release of bFGF. Twenty beagle dogs were randomly split into four groups: a) control group (n = 5), b) porcine pancreatic elastase (PPE)-induced emphysema group (n = 5), c) FGF-MS group [n = 5, a suspension of bFGF-incorporated gelatin microspheres (MS) was injected via the pulmonary artery of emphysema model animals], and d) MS group (n = 5, MS without bFGF were injected). Four weeks after injection, the treated lungs were observed histologically, and the mean linear intercept (Lm) was calculated in each group. Lm in the FGF-MS and MS groups was significantly smaller than that in the emphysema group (p < 0.0001), and the size of the dilated alveoli was similar to that in the control group. These changes were more evident in the FGF-MS group, where almost normal alveoli and dense microvascularization were observed around the small pulmonary arteries. Reconstruction of emphysematous lungs was achieved by intrapulmonary arterial administration of MS with or without bFGF. This method may allow trans-pulmonary arterial therapy for pulmonary emphysema.

Alpha-1 antitrypsin deficiency: a conformational disease associated with lung and liver manifestations

Alpha-1 antitrypsin (A1AT) is a serine anti-protease produced chiefly by the liver. A1AT deficiency is a genetic disorder characterized by serum levels of less than 11 mumol/L and is associated with liver and lung manifestations. The liver disease, which occurs in up to 15% of A1AT-deficient individuals, is a result of toxic gain-of-function mutations in the A1AT gene, which cause the A1AT protein to fold aberrantly and accumulate in the endoplasmic reticulum of hepatocytes. The lung disease is associated with loss-of-function, specifically decreased anti-protease protection on the airway epithelial surface. The so-called 'Z' mutation in A1AT deficiency encodes a glutamic acid-to-lysine substitution at position 342 in A1AT and is the most common A1AT allele associated with disease. Here we review the current understanding of the molecular pathogenesis of A1AT deficiency and the best clinical management protocols.

Lung MRI for experimental drug research

Current techniques to evaluate the efficacy of potential treatments for airways diseases in preclinical models are generally invasive and terminal. In the past few years, the flexibility of magnetic resonance imaging (MRI) to obtain anatomical and functional information of the lung has been explored with the scope of developing a non-invasive approach for the routine testing of drugs in models of airways diseases in small rodents. With MRI, the disease progression can be followed in the same animal. Thus, a significant reduction in the number of animals used for experimentation is achieved, as well as minimal interference with their well-being and physiological status. In addition, under certain circumstances the duration of the observation period after disease onset can be shortened since the technique is able to detect changes before these are reflected in parameters of inflammation determined using invasive procedures. The objective of this article is to briefly address MRI techniques that are being used in experimental lung research, with special emphasis on applications. Following an introduction on proton techniques and MRI of hyperpolarized gases, the attention is shifted to the MRI analysis of several aspects of lung disease models, including inflammation, ventilation, emphysema, fibrosis and sensory nerve activation. The next subject concerns the use of MRI in pharmacological studies within the context of experimental lung research. A final discussion points towards advantages and limitations of MRI in this area.

What have we learned from large drug treatment trials in COPD?

Although the development of effective treatments for patients with chronic obstructive pulmonary disease (COPD) has not been seen as a high priority, the past decade has seen a substantial increase in the number of clinical studies examining different treatments for this disease. Large studies are needed to adequately assess the effectiveness of treatment because of the chronic nature of the disease and the intermittent occurrence of some key outcomes such as exacerbations. Data from randomised controlled trials show that treatment improves exercise performance by increasing lung volume rather than changing expiratory flow. Although assessment of lung function remains the cornerstone of drug assessment, improvements in health status, the number of exacerbations and admissions to hospital are now recognised as important treatment outcomes. Randomised controlled trial data provide the best evidence for treatment efficacy, but results of these studies can be affected by differences in inclusion criteria and patient dropout during the study. Bronchodilator reversibility testing does not reliably define subgroups that will respond to a particular treatment. Carefully done and adequately powered clinical trials continue to inform, not only our views about treatment, but also our understanding of COPD and how it is best assessed and managed. Ensuring that these expensive studies are done objectively to the highest standard is an important goal for the next decade.

Thioredoxin prevents the development and progression of elastase-induced emphysema

Thioredoxin 1 (TRX1) is a redox (reduction/oxidation)-active protein that scavenges reactive oxygen species. Here we examined whether endogenous or exogenous administration of TRX1 prevented the development and progression of elastase-induced pulmonary emphysema. Mice were treated with intratracheal elastase via microspray on day 0, and were given recombinant human TRX1 (rhTRX1) every other day from days -1 to 21. To determine the effects of TRX1 on the progression of established emphysema, mice were treated intratracheally with elastase on day 0, and rhTRX1 was administered from days 14 to 21. Histopathologic examination was performed on day 21. TRX1-transgenic but not transgene-negative mice demonstrated a decrease in the physiological indicators of elastase-induced emphysema. TRX1 administration from days -1 to 19 significantly decreased the signs of elastase-induced emphysema. Moreover, TRX1 administration beginning 14 days after elastase treatment significantly slowed the progression of emphysema. TRX1 may be of clinical benefit for the treatment of COPD.

Pharmacokinetics of a novel agent, R667, in patients with emphysema

AIMS

To evaluate the pharmacokinetics of R667, a novel emphysema agent, in patients with moderate to severe emphysema.

METHODS

Multiple-dose pharmacokinetics of R667 and its metabolites in emphysematous patients were studied in a multicentre, randomized, single-blind, and placebo-controlled trial. Four groups of 10 patients per group received placebo, 0.2, 0.5, or 1 mg R667 once a day for 14-16 days. On day 14 (+/-1), blood samples were taken at predose and 1, 2, 3, 4, 6, 8, 10, 12, 16 and 24 h after dosing.

RESULTS

Pharmacokinetic analysis of the data indicated that the mean steady-state C(max) and AUC(0,tau) of R667 appeared to be dose proportional over the dose range of 0.2-1 mg when administered to emphysematous patients. Mean metabolite to R667 ratios for C(max) or AUC(0,tau) were, in general, similar across the dose range of 0.2-1 mg.

CONCLUSIONS

The pharmacokinetics of R667 and its metabolites appeared to be similar for patients with emphysema and healthy volunteers. Multiple-dose administration of 0.2-1 mg of R667 for up to 16 days was well tolerated in patients with emphysema.

The challenges of chronic obstructive pulmonary diseases (COPD)--a perspective

Chronic Obstructive Pulmonary Disease (COPD) is an inflammatory disease, primarily caused by cigarette smoke, which will soon become the third leading cause of death globally. Despite the importance of the problem, our real understanding of the biological underpinnings of COPD remains incomplete. Consequently, our first-line therapies, while helpful, are not yet as effective as they need to be. In this review, we will focus on these challenges and more, including the role of impaired tissue repair and adaptive immunity in disease pathogenesis, determining who may be at risk, describing COPD phenotypes and potential biomarkers. New ideas for chronic disease management and prevention of exacerbations will also be discussed. While much remains to be accomplished, meeting these challenges will bring rewards because what we learn will have implications for the understanding and treatment of chronic inflammatory diseases beyond COPD.

Advances in the management of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD), the fourth leading cause of death, seems to be increasing in worldwide prevalence, and carries with it a significant health and economic burden. Smoking cessation is the only available intervention proven to halt disease progression. The authors discuss the role of the newly approved agent, varenicline, in promotion of smoking cessation. The remainder of presently available therapies treat the symptoms of COPD, but do not impact progression of disease. As the understanding of the pathogenesis of COPD improves, new targets for therapies are emerging. Given the large number of potential targets and the results of recent studies, it seems unlikely that a single new agent will result in a cure. Rather, management of COPD should involve a multi-pronged approach including smoking cessation, bronchodilators, treatment of infection, and eventual targeting of inflammatory pathways and genetic predispositions. In this article, the authors discuss presently available therapies as well as agents under development.

Proton MRI as a noninvasive tool to assess elastase-induced lung damage in spontaneously breathing rats

Elastase-induced changes in lung morphology and function were detected in spontaneously breathing rats using conventional proton MRI at 4.7 T. A single dose of porcine pancreatic elastase (75 U/100 g body weight) or vehicle (saline) was administered intratracheally (i.t.) to male Brown Norway (BN) rats. MRI fluid signals were detected in the lungs 24 hr after administration of elastase and resolved within 2 weeks. These results correlated with perivascular edema and cellular infiltration observed histologically. Reductions in MRI signal intensity of the lung parenchyma, and increases in lung volume were detected as early as 2 weeks following elastase administration and remained uniform throughout the study, which lasted 8 weeks. Observations were consistent with air trapping resulting from emphysema detected histologically. In a separate experiment, animals were treated daily intraperitoneally (i.p.) with all-trans-retinoic acid (ATRA; 500 microg/kg body weight) or its vehicle (triglyceride oil) starting on day 21 after elastase administration and continuing for 12 days. Under these conditions, ATRA did not elicit a reversal of elastase-induced lung damage as measured by MRI and histology. The present approach complements other validated applications of proton MRI in experimental lung research as a method for assessing drugs in rat models of respiratory diseases.

Cigarette smoke inhibits alveolar repair: a mechanism for the development of emphysema

Classically, emphysema has been believed to develop when mediators of tissue injury exceed protective mechanisms within the lung. Evidence also supports the concept that tissue destruction represents a balance between tissue injury and tissue repair. In this context, cigarette smoke is directly toxic to cells within the lung and can impair the repair functions of fibroblasts, epithelial cells, and mesenchymal cells. This may occur in the absence of overt cytotoxicity and may result from alteration of selected biochemical pathways. A variety of repair functions can be affected, including chemotaxis, proliferation, production of extracellular matrix, and remodeling of extracellular matrix. Finally, cigarette smoke can damage DNA but can also compromise apoptosis. As a result, DNA repair mechanisms can be initiated, leading to recovery of cells that potentially contain somatic cell mutations. This pathway may contribute not only to the development of cancer but to the persistent abnormalities in tissue structure that characterize chronic obstructive pulmonary disease. Understanding the mechanisms that mediate normal tissue repair and understanding the bases for altered tissue repair in the face of cigarette smoking offer new opportunities designed to address the structural alterations that characterize chronic obstructive pulmonary disease.

Comparison of standard- and low-radiation-dose CT for quantification of emphysema

OBJECTIVE

This study was performed to compare standard- and low-radiation-dose techniques in the CT quantification of emphysema.

MATERIALS AND METHODS

The study population consisted of 36 men and 20 women who were current or former heavy smokers and underwent standard-dose (effective tube current, 100-250 mAs) chest CT at our institution within 6 months of having undergone low-dose (effective tube current, 30-60 mAs) chest CT. All CT scans were reconstructed at 5-mm slice thickness with a smooth filter. CT-measured lung volume, mean and median lung attenuation, and percentage of lung volume with attenuation lower than multiple thresholds (emphysema index values) were compared by Pearson correlation, two-tailed and paired Student's t tests, and regression analysis.

RESULTS

There were no significant differences in mean attenuation (-848 vs -846 H, p > 0.35) for the low dose and the standard dose or in median lung attenuation (-879 vs -878 H, p > 0.66). Low- and standard-dose emphysema indexes were correlated at all attenuation thresholds (r = 0.86-0.97). Mean emphysema indexes were higher on the low-dose scans, but the mean difference at all thresholds was less than 3%. The differences were significant (p < 0.05) only at the lower index thresholds, correlated with differences in lung volume (r < or = 0.86), and increased with greater differences in dose.

CONCLUSION

Low-dose technique has minimal effect on CT quantification of emphysema.

Vitamin A and emphysema

Within the last several years, research scientists and clinicians have been intrigued with the potential use of an active form of vitamin A, retinoic acid (RA), for the treatment and prevention of emphysema. The interest in this area can be largely attributed to the work of Massaro and Massaro (1996, 1997, 2000) in which they presented evidence that RA partially protects against and to some degree restores elastase-induced emphysema in rats. The mechanism for this protective effect of RA is in part related to elastin metabolism. RA also inhibits inflammation, an upstream event that may lead to the development of emphysema. Although there is evidence of this protective effect in young rats and a mechanistic explanation, more studies are needed in humans in order to establish a role for vitamin A in protecting against emphysema. Too many unanswered questions remain to definitively state that vitamin A protects against this disease in humans. Nevertheless, the potential for this novel approach in prevention and treatment of emphysema is an exciting area of research.

Feasibility of retinoids for the treatment of emphysema study

BACKGROUND

Retinoids promote alveolar septation in the developing lung and stimulate alveolar repair in some animal models of emphysema.

METHODS

One hundred forty-eight subjects with moderate-to-severe COPD and a primary component of emphysema, defined by diffusing capacity of the lung for carbon monoxide (Dlco) [37.1 +/- 12.0% of predicted] and CT density mask (38.5 +/- 12.8% of voxels <- 910 Hounsfield units) [mean +/- SD] were enrolled into a randomized, double-blind, feasibility study at five university hospitals. Participants received all-trans retinoic acid (ATRA) at either a low dose (LD) [1 mg/kg/d] or high dose (HD) [2 mg/kg/d], 13-cis retinoic acid (13-cRA) [1 mg/kg/d], or placebo for 6 months followed by a 3-month crossover period.

RESULTS

No treatment was associated with an overall improvement in pulmonary function, CT density mask score, or health-related quality of life (QOL) at the end of 6 months. However, time-dependent changes in Dlco (initial decrease with delayed recovery) and St. George Respiratory Questionnaire (delayed improvement) were observed in the HD-ATRA cohort and correlated with plasma drug levels. In addition, 5 of 25 participants in the HD-ATRA group had delayed improvements in their CT scores that also related to ATRA levels. Retinoid-related side effects were common but generally mild.

CONCLUSIONS

No definitive clinical benefits related to the administration of retinoids were observed in this feasibility study. However, time- and dose-dependent changes in Dlco, CT density mask score, and health-related QOL were observed in subjects treated with ATRA, suggesting the possibility of exposure-related biological activity that warrants further investigation.

Emerging drugs for the treatment of chronic obstructive pulmonary disease

By 2020 chronic obstructive pulmonary disease (COPD) will be the third leading cause of mortality and fifth leading cause of morbidity. Research over the past two decades has shed important insights on the pathobiology of COPD, leading to the development of novel drugs. In the past, symptomatic treatment with bronchodilators was the predominant focus of COPD management. With increased awareness of the importance of airway inflammation in COPD progression, there has been a shift in emphasis to drugs that attack various targets in the inflammatory cascade. These drugs include phosphodiesterase 4 inhibitors, leukotriene modifiers and TNF antagonists, which are poised to enter the COPD market in the very near future. Tyrosine kinase antagonists, inhibitors of NF-kappaB, neutrophil elastase inhibitors, chemokine antagonists, mucolytics and novel antibiotics are being evaluated for possible effectiveness in COPD. Many of these drugs may enter the COPD market within the next decade. This paper reviews the molecular rationale for these emerging drugs and their potential efficacy in COPD.

Modulators of cigarette smoke-induced pulmonary emphysema in A/J mice

Mice develop pulmonary emphysema after chronic exposure to cigarette smoke (CS). In this study, the influence of gender, exposure duration, and concentration of CS on emphysema, pulmonary function, inflammation, markers of toxicity, and matrix metalloproteinase (MMP) activity was examined in A/J mice. Mice were exposed to CS at either 100 or 250 mg total particulate material/m(3) (CS-100 or CS-250, respectively) for 10, 16, or 22 weeks. Evidence of emphysema was first seen in female mice after 10 weeks of exposure to CS-250, while male mice did not develop emphysema until 16 weeks. Female mice exposed to CS-100 did not have emphysema until 16 weeks, suggesting that disease development depends on the concentration and duration of exposure. Airflow obstruction and increased pulmonary compliance were observed in mice exposed to CS-250 for 22 weeks. Decreased elasticity was likely the major contributor to airflow obstruction because substantial remodeling of the conducting airways, beyond mild mucous cell hyperplasia, was lacking. Exposure to CS increased the number of macrophages, neutrophils, lymphocytes (B cells and activated CD4- and CD8-positive T cells), and activity of MMP-2 and -9 in the bronchoalveolar lavage fluid (BALF). Treatment with antioxidants N-acetylcysteine or epigallocatechin gallate (EGCG) did not decrease emphysema severity, but EGCG slightly decreased BALF inflammatory cell numbers and lactate dehydrogenase activity. Inflammation and emphysema persisted after a 17-week recovery period following exposure to CS-250 for 22 weeks. The similarities of this model to the human disease make it promising for studying disease pathogenesis and assessing new therapeutic interventions.

The Epithelial Cell in Lung Health and Emphysema Pathogenesis

Cigarette smoking is the primary cause of the irreversible lung disease emphysema. Historically, inflammatory cells such as macrophages and neutrophils have been studied for their role in emphysema pathology. However, recent studies indicate that the lung epithelium is an active participant in emphysema pathogenesis and plays a critical role in the lung's response to cigarette smoke. Tobacco smoke increases protease production and alters cytokine expression in isolated epithelial cells, suggesting that these cells respond potently even in the absence of a complete inflammatory program. Tobacco smoke also acts as an immunosuppressant, reducing the defense function of airway epithelial cells and enhancing colonization of the lower airways. Thus, the paradigm that emphysema is strictly an inflammatory-cell based disease is shifting to consider the involvement of resident epithelial cells. Here we review the role of epithelial cells in lung development and emphysema. To better understand tobacco-epithelial interactions we performed microarray analyses of RNA from human airway epithelial cells exposed to smoke extract for 24 hours. These studies identified differential regulation of 425 genes involved in diverse biological processes, such as apoptosis, immune function, cell cycle, signal transduction, proliferation, and antioxidants. Some of these genes, including VEGF, glutathione peroxidase, IL-13 receptor, and cytochrome P450, have been previously reported to be altered in the lungs of smokers. Others, such as pirin, cathepsin L, STAT1, and BMP2, are shown here for the first time to have a potential role in smoke-associated injury. These data broaden our understanding of the importance of epithelial cells in lung health and cigarette smoke-induced emphysema.

Mediator mechanisms involved in TRPV1 and P2X receptor-mediated, ROS-evoked bradypneic reflex in anesthetized rats

Inhalation of H2O2 is known to evoke bradypnea followed by tachypnea, which are reflexes resulting from stimulation by reactive oxygen species of vagal lung capsaicin-sensitive and myelinated afferents, respectively. This study investigated the pharmacological receptors and chemical mediators involved in triggering these responses. The ventilatory responses to 0.2% aerosolized H2O2 were studied before and after various pharmacological pretreatments in anesthetized rats. The initial bradypneic response was reduced by a transient receptor potential vanilloid 1 (TRPV1) receptor antagonist [capsazepine; change (Delta) = -53%] or a P2X purinoceptor antagonist [iso-pyridoxalphosphate-6-azophenyl-2',5'-disulphonate (PPADS); Delta = -47%] and was further reduced by capsazepine and iso-PPADS in combination (Delta = -78%). The initial bradypneic response was reduced by a cyclooxygenase inhibitor (indomethacin; Delta = -48%), ATP scavengers (apyrase and adenosine deaminase in combination; Delta = -50%), or capsazepine and indomethacin in combination (Delta = -47%), was further reduced by iso-PPADS and indomethacin in combination (Delta = -75%) or capsazepine and ATP scavengers in combination (Delta = -83%), but was not affected by a lipoxygenase inhibitor (nordihydroguaiaretic acid) or by any of the various vehicles. No pretreatment influenced delayed tachypnea. We concluded that 1) the initial bradypneic response to H2O2 results from activation of both TRPV1 and P2X receptors, possibly located at terminals of vagal lung capsaicin-sensitive afferent fibers; 2) the functioning of the TRPV1 and P2X receptors in triggering the initial bradypnea is, in part, mediated through the actions of cyclooxygenase metabolites and ATP, respectively; and 3) these mechanisms do not contribute to the H2O2-evoked delayed tachypnea.

Gene therapy for chronic obstructive pulmonary disease: twilight or triumph?

Chronic obstructive pulmonary disease (COPD) is a clinical syndrome presenting as progressive airflow limitation that is poorly reversible as a result of bronchitis and emphysema. The prevalence of COPD is alarming and even more so its current and projected impact on morbidity and mortality. To date, there are no effective treatments for emphysema, nor are there efficient clinical management strategies. Existing and prospective therapies, although promising, have yet to demonstrate their efficacy to slow, halt or reverse the disease. Novel approaches using gene therapy and stem cell technologies may offer new opportunities. However, this will remain almost entirely dependent on a more thorough understanding of the pathogenesis of COPD. This review is not aimed at highlighting the vast effort of studying COPD, but rather describing the state of the field in an abstract fashion to expose the focus of research efforts to date, which has primarily been limited to predisposing factors and inflammation. We would like to draw attention to other elements of the disease, such as the alveolar remodelling that characterises emphysema. Although the main cause may prove to be elusive, carefully designed clinical treatment and management may deliver the required therapeutic outcome.

Quantitative computed tomography of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is described as airflow limitation that is not fully reversible. Quantitative assessment of structural changes within the lung that are responsible for this airflow limitation has relied on the examination of tissue obtained from surgical or postmortem specimens. However, in the past two decades, researchers have developed novel and robust tools to measure the structure of the lung parenchyma and airway wall by using computed tomographic (CT) scans, which do not require the removal of lung tissue. These techniques are extremely important because they allow longitudinal studies of the pathogenesis of COPD and the assessment of therapeutic interventions. Another application of this approach is that it potentially allows phenotyping of individuals who predominately have emphysema or small-airway disease, which may be important for the evaluation of pathogenesis and prescription of treatment options. This review describes some of these CT techniques for quantitative assessment of lung structure.

Use of CT Morphometry To Detect Changes in Lung Weight and Gas Volume

STUDY OBJECTIVES

CT estimates of lung density have been used to estimate the extent and severity of emphysema. The present study was designed to test the hypothesis that quantitative CT can track the changes that occur in diffuse lung disease.

DESIGN

The study was based on five patients with pulmonary alveolar proteinosis (PAP) who underwent lung lavage. Pulmonary function was measured before and after each individual lung lavage, and the CT scans before and after lavage were used to compare total lung volume, airspace volume, lung weight, and regional lung inflation. The dry weight of proteinaceous material lavaged from the lung was measured and compared to the change in CT lung weight.

RESULTS

All the patients showed improvements in dyspnea, percentage of predicted diffusion capacity of the lung for carbon monoxide, and FVC. There was no change in CT-measured total lung volume or airspace volume, but there was a reduction in lung weight following lavage (p = 0.001), which correlated with the dry weight of the lavage effluent (R(2) = 0.73). Therefore, there was a shift in the regional lung inflation toward a more inflated lung with a corresponding increase in the mean lung inflation (p = 0.001).

CONCLUSION

These data show that quantitative CT can objectively track the changes in lung weight and airspace inflation produced by a standard intervention in PAP, and we postulate that it can provide similar information about the progression of other diffuse lung diseases.

Steroid-resistant Inflammation in a Rat Model of Chronic Obstructive Pulmonary Disease Is Associated with a Lack of Nuclear Factor-κB Pathway Activation

RATIONALE

Emphysema is one component of chronic obstructive pulmonary disease (COPD), a respiratory disease currently increasing in prevalence worldwide. The mainstay therapy adopted to treat patients with COPD is glucocorticoids; unfortunately, this treatment has limited impact on disease symptoms or underlying airway inflammation.

OBJECTIVE

There is an urgent need to develop therapies that modify both the underlying inflammation, thought to be involved in disease progression, and the structural changes in the emphysematous lung.

METHODS

We have characterized an elastase-driven model of experimental emphysema in the rat that demonstrates COPD-like airway inflammation and determined the impact of a clinically relevant glucocorticoid.

MEASUREMENTS AND MAIN RESULTS

We observed an increase in lung neutrophils, lymphomononuclear cells, mucus production, and inflammatory cytokines. Also present were increases in average air space area, which are associated with emphysema-like changes in lung function, such as increased residual volume and decreased flow; these increases in area were maintained for up to 10 weeks. In addition, we observed that elastase-induced airway neutrophilia is steroid resistant. Interestingly, the inflammation observed after elastase administration was found to be temporally associated with a lack of nuclear factor-kappaB pathway activation. This apparent nuclear factor-kappaB-independent inflammation may explain why treatment with a glucocorticoid was ineffective in this preclinical model and could suggest parallels in the steroid-resistant human disease.

CONCLUSION

We believe that this model, in addition to its suitability for testing therapies that may modify existing emphysema, could be useful in the search for new therapies to reduce the steroid-resistant airway inflammation evident in COPD.

Enfermedad pulmonar obstructiva crónica

Treatment of chronic obstructive pulmonary disease (COPD) has underwent a very important advance in the last five years. It has been developed a new long-lasting anticholynergic drug, tiotrope bromure, which has been found to improve lung function and exercise capacity and to decrease relapses. Also the combined treatment of long lasting beta 2 adrenergics with inhaled steroids (salmeterol/fluticasone and formoterol/budesonide) has proven similar results. However, the response to these new drugs is not the same in all patients. Individual characteristics such as gravity, degree of bronchial hyperresponsiveness, frequency of relapses, comorbidity, etc will determine the response to several agents. Thus, it is necessary to perform a detailed diagnostic study in COPD patients in order to select the best treatment in an individualized form. In the future, new specific antiinflammatories such as phosphodiesterase 4 inhibitors or agents with a potential action in tissue regeneration could lead to new perspectives, as well as to new questions, in COPD treatment.

Database Design and Implementation for Quantitative Image Analysis Research

Quantitative image analysis (QIA) goes beyond subjective visual assessment to provide computer measurements of the image content, typically following image segmentation to identify anatomical regions of interest (ROIs). Commercially available picture archiving and communication systems focus on storage of image data. They are not well suited to efficient storage and mining of new types of quantitative data. In this paper, we present a system that integrates image segmentation, quantitation, and characterization with database and data mining facilities. The paper includes generic process and data models for QIA in medicine and describes their practical use. The data model is based upon the Digital Imaging and Communications in Medicine (DICOM) data hierarchy, which is augmented with tables to store segmentation results (ROIs) and quantitative data from multiple experiments. Data mining for statistical analysis of the quantitative data is described along with example queries. The database is implemented in PostgreSQL on a UNIX server. Database requirements and capabilities are illustrated through two quantitative imaging experiments related to lung cancer screening and assessment of emphysema lung disease. The system can manage the large amounts of quantitative data necessary for research, development, and deployment of computer-aided diagnosis tools.

COPD, a multicomponent disease: implications for management

Chronic obstructive pulmonary disease (COPD) is a multicomponent disease. These components affect both the lungs and organs outside the lungs (the so-called systemic effects of COPD) and can be of either a structural (including airway remodelling, emphysema, skeletal muscle wasting) or functional nature (inflammation, apoptosis, senescence). Further, these components are interdependent in a closely linked 'vicious cycle'. Accordingly, optimal therapies should therefore aim to address more than one of these components to break such a cycle. This needs to be considered not only in the development of future treatments but also in the current clinical management of patients with COPD. In this paper, evidence that supports the concept that COPD is a multicomponent disease is presented. The effects of currently available therapeutic options, including long-acting anticholinergics and long-acting beta2-agonist/inhaled corticosteroid combination therapies, upon each of these components is reviewed. In addition, potential new avenues for drug development and improved patient care are highlighted. By developing a better understanding of how different therapies impact upon the 'vicious cycle' of COPD, treatment regimens can be optimised to provide the greatest benefits to patients.

Stem cells and pulmonary metamorphosis: New concepts in repair and regeneration

Adult stem cells are likely to have much more versatile differentiation capabilities than once believed. Numerous studies have appeared over the past decade demonstrating the ability of adult stem cells to differentiate into a variety of cells from non-hematopoietic organs, including the lung. The goal of this review is to provide an overview of the growth factors which are thought to be involved in lung development and disease, describe the cells within the lung that are believed to replace cells that have been injured, review the studies that have demonstrated the transformation of bone marrow-derived stem cells into lung cells, and describe potential clinical applications with respect to human pulmonary disease.

Models of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a major global health problem and is predicted to become the third most common cause of death by 2020. Apart from the important preventive steps of smoking cessation, there are no other specific treatments for COPD that are as effective in reversing the condition, and therefore there is a need to understand the pathophysiological mechanisms that could lead to new therapeutic strategies. The development of experimental models will help to dissect these mechanisms at the cellular and molecular level. COPD is a disease characterized by progressive airflow obstruction of the peripheral airways, associated with lung inflammation, emphysema and mucus hypersecretion. Different approaches to mimic COPD have been developed but are limited in comparison to models of allergic asthma. COPD models usually do not mimic the major features of human COPD and are commonly based on the induction of COPD-like lesions in the lungs and airways using noxious inhalants such as tobacco smoke, nitrogen dioxide, or sulfur dioxide. Depending on the duration and intensity of exposure, these noxious stimuli induce signs of chronic inflammation and airway remodelling. Emphysema can be achieved by combining such exposure with instillation of tissue-degrading enzymes. Other approaches are based on genetically-targeted mice which develop COPD-like lesions with emphysema, and such mice provide deep insights into pathophysiological mechanisms. Future approaches should aim to mimic irreversible airflow obstruction, associated with cough and sputum production, with the possibility of inducing exacerbations.

alpha1-Antitrypsin deficiency . 6: new and emerging treatments for alpha1-antitrypsin deficiency

Alpha-1-antitrypsin (AAT) deficiency is a genetic condition that increases the risk of developing lung and liver disease, as well as other associated conditions. Most treatment of affected individuals is not specifically directed at AAT deficiency but focuses on the resultant disease state. The only currently available specific therapeutic agent-namely, intravenous augmentation with plasma derived AAT protein-is marketed in a limited number of countries. Treatments aimed at correcting the underlying genetic abnormality, supplementing or modifying the gene product, and halting or reversing organ injury are now beginning to emerge. These innovative approaches may prove effective at modifying or eliminating diseases association with AAT deficiency.

The involvement of hydroxyl radical and cyclooxygenase metabolites in the activation of lung vagal sensory receptors by circulatory endotoxin in rats

Circulatory endotoxin can stimulate vagal pulmonary C fibers and rapidly adapting receptors (RARs) in rats, but the underlying mechanisms are not clear. We investigated the involvement of hydroxyl radicals and cyclooxygenase metabolites in the stimulation of C fibers and RARs by circulatory endotoxin (50 mg/kg) in 112 anesthetized, paralyzed, and artificially ventilated rats. In rats pretreated with the vehicle, endotoxin stimulated C fibers and RARs and caused a slight increase in total lung resistance (Rl) and a decrease in dynamic lung compliance. In rats pretreated with dimethylthiourea (a hydroxyl radical scavenger) alone, indomethacin (a cyclooxygenase inhibitor) alone, or a combination of the two, C-fiber and RAR responses [C fiber: change (Delta) = -62, -79, and -85%; RAR: Delta = -80, -84, and -84%, respectively] were reduced, and the Rl response was prevented. The suppressive effects of a combination of dimethylthiourea and indomethacin on the C-fiber and RAR responses were not superior to indomethacin alone. In rats pretreated with isoproterenol (a bronchodilator), the C-fiber response was not significantly affected (Delta = -26%), the RAR response was reduced (Delta = -88%), and the Rl response was prevented. None of these pretreatments affected the dynamic lung compliance response. These results suggest that 1) both hydroxyl radicals and cyclooxygenase metabolites are involved in the endotoxin-induced stimulation of C fibers and RARs, and 2) the involvement of these two metabolites in the C-fiber stimulation may be due to their chemical effects, whereas that in the RAR stimulation may be due to their bronchoconstrictive effects.

Prospects for new drugs for chronic obstructive pulmonary disease

No currently available treatments have been shown to slow the progression of chronic obstructive pulmonary disease (COPD) or suppress the inflammation in small airways and lung parenchyma. However, several new treatments are in clinical development; some target the inflammatory process and others are directed against structural cells. A group of specific therapies are directed against the influx of inflammatory cells into the airways and lung parenchyma that occurs in COPD; these include agents directed against adhesion molecules and chemokines, as well as therapies to oppose tumour necrosis factor alpha and increase interleukin 10. Broad-range anti-inflammatory drugs are now in phase III development for COPD; they include inhibitors of phosphodiesterase 4. Other drugs that inhibit cell signalling include inhibitors of p38 mitogen-activated protein kinase, nuclear factor kappaB, and phosphoinositide-3-kinase gamma. More specific approaches are to give antioxidants, inhibitors of inducible nitric oxide synthase, and antagonists of leukotriene B4 receptor. Inhibitors of epidermal-growth-factor-receptor kinase and calcium-activated chloride channels have the potential to prevent overproduction of mucus. Therapy to inhibit fibrosis is being developed against transforming growth factor beta1 and protease-activated receptor 2. There is also a search for inhibitors of serine proteinases and matrix metalloproteinases to prevent lung destruction and the development of emphysema, as well as drugs such as retinoids that might even reverse this process. Effective delivery of drugs to the sites of disease in the peripheral lung is an important consideration, and there is a need for validated biomarkers and monitoring techniques in early clinical studies with new therapies for COPD.

Therapy for chronic obstructive pulmonary disease in the 21st century

Chronic obstructive pulmonary disease (COPD) is a common, smoking-related, severe respiratory condition characterised by progressive, irreversible airflow limitation. Current treatment of COPD is symptomatic, with no drugs capable of halting the relentless progression of airflow obstruction. Better understanding of the airway inflammation, oxidative stress and alveolar destruction that characterise COPD has delineated new disease targets, with consequent identification of novel compounds with therapeutic potential. These new drugs include aids to smoking cessation (e.g. bupropion) and improvements to existing therapies, for example long-acting rather than short-acting bronchodilators, as well as combination therapy. New antiproteases include acyl-enzyme and transition state inhibitors of neutrophil elastase (e.g. sivelestat and ONO-6818), matrix metalloprotease inhibitors (e.g. batimastat), cathepsin inhibitors and peptide protease inhibitors (e.g. DX-890 [EPI-HNE-4] and trappin-2). New antioxidants include superoxide dismutase mimetics (e.g. AEOL-10113) and spin trap compounds (e.g. N-tert-butyl-alpha-phenylnitrone). New anti-inflammatory interventions include phosphodiesterase-4 inhibitors (e.g. cilomilast), inhibitors of tumour necrosis factor-alpha (e.g. humanised monoclonal antibodies), adenosine A(2a) receptor agonists (e.g. CGS-21680), adhesion molecule inhibitors (e.g. bimosiamose [TBC1269]), inhibitors of nuclear factor-kappaB (e.g. the naturally occurring compounds hypoestoxide and (-)-epigallocatechin-3-gallate) and activators of histone deacetylase (e.g. theophylline). There are also selective inhibitors of specific extracellular mediators such as chemokines (e.g. CXCR2 and CCR2 antagonists) and leukotriene B(4) (e.g. SB201146), and of intracellular signal transduction molecules such as p38 mitogen activated protein kinase (e.g. RWJ67657) and phosphoinositide 3-kinase. Retinoids may be one of the few potential treatments capable of reversing alveolar destruction in COPD, and a number of compounds are in clinical trial (e.g. all-trans-retinoic acid). Talniflumate (MSI-1995), an inhibitor of human calcium-activated chloride channels, has been developed to treat mucous hypersecretion. In addition, the purinoceptor P2Y(2) receptor agonist diquafosol (INS365) is undergoing clinical trials to increase mucus clearance. The challenge to transferral of these new compounds from preclinical research to disease management is the design of effective clinical trials. The current scarcity of well characterised surrogate markers predicts that long-term studies in large numbers of patients will be needed to monitor changes in disease progression.

Retinoic acid fails to reverse emphysema in adult mouse models

BACKGROUND

Previous work has shown that all-trans-retinoic acid reverses elastase induced emphysema in rats. Since there is currently no effective treatment for pulmonary emphysema, the effect of retinoic acid should be further investigated in other adult species. A study was undertaken using two murine models of emphysema to evaluate the effect of retinoic acid.

METHODS

The models used were an elastase induced emphysema model for acute alveolar destruction and a tumour necrosis factor (TNF)-alpha transgenic mouse which exhibits chronic air space enlargement, loss of elastic recoil, increased lung volume, and pulmonary hypertension comparable to human pulmonary emphysema. All-trans-retinoic acid (2 mg/kg) was injected for 12 successive days after the establishment of emphysema. The effects of treatment were evaluated using physiological and morphometric analyses.

RESULTS

In contrast to the rat, administration of all-trans-retinoic acid in these murine models did not improve the emphysema. Moreover, worsening of emphysema was observed in TNF-alpha transgenic mice treated with all-trans-retinoic acid. The level of keratinocyte chemoattractant (KC), a CXC chemokine, in bronchoalveolar lavage fluid was increased in TNF-alpha transgenic mice following retinoic acid treatment. These data raise the possibility that retinoic acid causes deterioration of emphysema by promoting inflammation in this model.

CONCLUSIONS

In these models, retinoic acid did not show positive effects on emphysema. The effect of retinoic acid in the treatment of pulmonary emphysema remains controversial, and further studies are required to determine its physiological effects under a variety of experimental conditions.

Bone marrow-derived cells contribute to lung regeneration after elastase-induced pulmonary emphysema

All-trans retinoic acid (ATRA) is known to reverse the anatomic and physiologic signs of pulmonary emphysema. However, the origin of the progenitor cells involved in this lung regeneration remains unclear. Recently, it was shown that bone marrow could be the source of progenitor cells for several cell types. Mice with elastase-induced emphysema were treated with ATRA, granulocyte colony-stimulating factor (G-CSF), or a combination of both. ATRA or G-CSF promoted lung regeneration and increased bone marrow-derived cell (BMC) numbers in alveoli. Combined treatment of both had an additive effect, which indicated that BMC mobilization might be important in lung regeneration.

Retinoic acid-induced alveolar cellular growth does not improve function after right pneumonectomy

To determine whether all- trans retinoic acid (RA) treatment enhances lung function during compensatory lung growth in fully mature animals, adult male dogs ( n = 4) received 2 mg·kg-1·day-1po RA 4 days/wk beginning the day after right pneumonectomy (R-PNX, 55-58% resection). Litter-matched male R-PNX controls ( n = 4) received placebo. After 3 mo, transpulmonary pressure (TPP)-lung volume relationship, diffusing capacities for carbon monoxide and nitric oxide, cardiac output, and septal volume (Vtiss-RB) were measured under anesthesia by a rebreathing technique at two lung volumes. Lung air and tissue volumes (Vair-CTand Vtiss-CT) were also measured from high-resolution computerized tomographic (CT) scans at a constant TPP. In RA-treated dogs compared with controls, TPP-lung volume relationships were similar. Diffusing capacities for carbon monoxide and nitric oxide were significantly impaired at a lower lung volume but similar at a high lung volume. Whereas Vtiss-RBwas significantly lower at both lung volumes in RA-treated animals, Vair-CTand Vtiss-CTwere not different between groups; results suggest uneven distribution of ventilation consistent with distortion of alveolar geometry and/or altered small airway function induced by RA. We conclude that RA does not improve resting pulmonary function during the early months after R-PNX despite histological evidence of its action in enhancing alveolar cellular growth in the remaining lung.

Retinoic acid induces nonuniform alveolar septal growth after right pneumonectomy

To determine whether all- trans retinoic acid (RA) enhances compensatory lung growth in fully mature animals, adult male dogs ( n = 4) received 2 mg·kg-1·day-1 po RA 4 days/wk beginning the day after right pneumonectomy (R-PNX, 55-58% resection). Litter-matched male R-PNX controls ( n = 4) received placebo. After 4 mo, the remaining lung was fixed by tracheal instillation of fixatives at a constant airway pressure for detailed morphometric analysis. After RA treatment compared with placebo, lung volume was slightly but not significantly lower. Volume density of septum to lung was 37% higher because of a 50 and 25% higher volume density of capillary and septal tissue, respectively. Mean septal thickness was 27% higher. Absolute volumes of endothelial cells and capillary blood were 31-37% higher, whereas epithelial and interstitial volumes were not different between groups. Absolute alveolar-capillary surface areas did not differ between groups, and alveolar septal surface-to-volume ratio was 20% lower in RA-treated animals. RA treatment exaggerated interlobar differences in morphometric indexes and caused alveolar capillary morphology to revert to a more immature state. Thus RA treatment during early post-R-PNX adaptation preferentially enhanced alveolar capillary and endothelial cell volumes consistent with formation of new capillaries, but the associated septal distortion precluded a corresponding increase in gas-exchange surface or morphometric estimates of lung diffusing capacity.