![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
![[Contents]](/icons/banner/tocACT.gif){kind=icon}
|
|
|
|
|
||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
INFLAMMATION AND IMMUNOPHARMACOLOGY
Department of Pathology (R.K.K., C.H.) and Prince of Wales Hospital Clinical School (P.S.T.), University of New South Wales, Sydney, Australia; Department of Pharmacology, ALTANA Pharma AG, Konstanz, Germany (L.W., R.B.); and Division of Molecular Biosciences, John Curtin School of Medical Research, Australian National University, Canberra, Australia (M.Y., D.C.W., P.S.F.)
Received May 4, 2003; accepted June 30, 2003.
 |
Abstract |
|---|
 Top Abstract Materials and MethodsResultsDiscussionReferences |
|---|
1, and epithelial cytoplasmic immunoreactivity for nuclear factor-
B. Treatment with pentoxifylline inhibited only eosinophil recruitment and epithelial thickening. Roflumilast and dexamethasone slightly decreased AHR, whereas this was significantly reduced by pentoxifylline. Thus, in this model of chronic asthma, both roflumilast and dexamethasone were potent inhibitors of airway inflammation and remodeling. Roflumilast did not diminish accumulation of transforming growth factor-1, suggesting that it might affect remodeling by mechanisms distinct from glucocorticoids.
; Howarth, 2001; Kumar, 2001). Changes of remodeling correlate with the development of airway hyper-reactivity (AHR) (Chetta et al., 1996; Hoshino et al., 1998a; Howarth, 2001) and with persistent airflow limitation in chronic asthmatics (Niimi et al., 2000). The progressive decline in lung function may be inhibited by maintenance therapy with inhaled glucocorticoids, presumably because of inhibition of the progression of airway wall remodeling (Howarth, 2001). Moreover, long-term titration of inhaled glucocorticoid therapy to reduce AHR, which yields substantially improved clinical outcomes, is associated with significant reduction in subepithelial fibrosis (Sont et al., 1999). These observations lend support to the notion that therapeutic agents able to efficiently inhibit airway wall remodeling may be of particular value in asthma.
Phosphodiesterase (PDE) isoenzymes control the degradation of cyclic AMP and thus play key roles in regulating compartmentalized signaling responses to intracellular gradients of cyclic AMP (Houslay and Adams, 2003). The PDE4 family of enzymes, encoded by four PDE4 genes, which generate at least 16 different isoforms, exclusively hydrolyzes cyclic AMP and accounts for most of this activity within cells (Conti et al., 2003; Houslay and Adams, 2003). Selective inhibitors of PDE4, which are directed against the catalytically active site, inhibit the function of a variety of inflammatory and immunomodulatory cells (Torphy, 1998). For example, these compounds decrease the production of numerous relevant inflammatory mediators, including histamine and leukotrienes (Weston et al., 1997), proinflammatory cytokines such as tumor necrosis factor-
and interleukin-1 (Verghese et al., 1995), as well as T-lymphocyte-derived cytokines such as interleukin-4 and -5 (Souness et al., 1999).
The potential value of selective PDE4 inhibitors in the treatment of inflammatory disease of the airways has been demonstrated in preliminary studies of their use in chronic obstructive pulmonary disease (Compton et al., 2001). PDE4 inhibitors may also be useful as alternatives or adjuncts to glucocorticoids in the treatment of asthma because they exhibit significant anti-inflammatory activity in a variety of in vivo models of allergic bronchopulmonary inflammation (Schudt et al., 1995; Torphy, 1998). Nevertheless, assessment of their capacity to modulate airway wall remodeling has hitherto been limited by the lack of a suitable model of chronic asthma that replicates these structural changes.
We have described an experimental model of asthma in mice, in which BALB/c mice are systemically sensitized to ovalbumin and subjected to inhalational challenge with low mass concentrations of aerosolized antigen for at least 6 weeks (Temelkovski et al., 1998). This model replicates most of the features that are typical of the chronic human disease, including accumulation of numerous intraepithelial eosinophils, chronic inflammation in the lamina propria, together with epithelial hypertrophy, mucous cell hyperplasia/metaplasia, and subepithelial fibrosis. Unlike other chronic exposure models, there is no evidence of down-regulation of inflammatory or immunologic responses. Furthermore, there is no associated parenchymal inflammation so that development of AHR can be attributed to abnormalities of the airways rather than to parenchymal lesions. Using gene-targeted animals and long-term administration of antibodies, we have employed this model to investigate the role of various mediators and cell populations in the pathogenesis of chronic asthma (reviewed in Kumar and Foster, 2002).
In the present study, we examined the ability of roflumilast, a novel potent PDE4-selective inhibitor (Hatzelmann and Schudt, 2001), to inhibit airway inflammation, remodeling, and AHR in this model. Roflumilast has been demonstrated to be an effective anti-inflammatory agent in acute allergen challenge models in animals and is capable of inhibiting antigen-induced bronchospasm (Bundschuh et al., 2001). Its potential usefulness in human asthma has been demonstrated in clinical studies (Timmer et al., 2002). We compared the therapeutic response to roflumilast with that to pentoxifylline (a nonspecific PDE inhibitor) and the glucocorticoid dexamethasone and investigated the effects of these drugs on underlying mechanisms potentially involved in airway inflammation and remodeling.
|
Materials and Methods |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
; Foster et al., 2000; Kumar et al., 2002). Briefly, specific pathogen-free female BALB/c mice (aged approximately 8 weeks at the commencement of experimental studies) were sensitized by intraperitoneal injections of 50 µg of alum-precipitated chicken egg ovalbumin (Sigma Australia, Sydney, Australia; unless otherwise specified, all chemicals were obtained from this source) 21 days and 7 days before inhalational exposure. They were maintained in a laminar flow holding unit (Gelman Sciences, Sydney, Australia) and housed in autoclaved cages on autoclaved bedding in an air-conditioned room on a 12-h light/dark cycle. Irradiated food and acidified water were provided ad libitum throughout. Mice were exposed to 10 to 20 mg/m3 of aerosolized ovalbumin for 30 min/day on 3 days/week for 6 weeks in a whole-body inhalation exposure chamber (Unifab Corporation, Kalamazoo, MI). All experimental procedures complied with the Australian Code of Practice for the Care and Use of Animals for Scientific Purposes and additional requirements of the Animal Care and Ethics Committee of the University of New South Wales (reference 01/34.1).
Groups of eight animals were treated with roflumilast (ALTANA Pharma, Konstanz, Germany) (5 mg/kg/day by gavage, suspended in 2.5% polyethylene glycol-4% methylcellulose solution), dexamethasone (1 mg/kg/day by gavage, cyclodextrin compound in saline), or pentoxifylline (50 mg/kg/day by intraperitoneal injection, in saline) on 5 days/week for the last 2 weeks of the inhalational exposure. For each of these drugs, this was the lowest dosage that was effective in inhibiting an inflammatory response. The dosage of roflumilast was based on studies of its anti-inflammatory activity in a model of collagen-induced arthritis in mice (Barsig et al., 2001) and on kinetic studies which demonstrated that 5 mg/kg/day produces therapeutically relevant blood levels in these animals (ALTANA Pharma, unpublished data). The dosages of pentoxifylline and dexamethasone, which are similar to those used in other investigations of their anti-inflammatory effects (Kremsner et al., 1991; Blyth et al., 1998), were selected on the basis of preliminary experiments in the chronic asthma model in which a range of doses was compared with the ability to inhibit accumulation of eosinophils and/or chronic inflammatory cells. These experiments also established that pentoxifylline was relatively ineffective when administered to mice by gavage. Drugs were administered 30 min before aerosol challenge. Vehicle-treated control animals received polyethylene glycol-methylcellulose by gavage and naive unexposed controls of the same age were assessed in parallel. We have previously shown that sensitized and chronically exposed control animals treated with intraperitoneal injections of saline develop lesions comparable to those of untreated animals (C. Herbert and R. K. Kumar, unpublished data) and that chronic exposure of nonsensitized mice is not associated with development of significant airway inflammation, remodeling, or AHR (Foster et al., 2000).
Airway Reactivity. As a screening procedure for the assessment of changes in airway reactivity, responsiveness to methacholine was assessed in conscious, unrestrained mice by whole-body plethysmography (Buxco, Troy, NY) approximately 24 h after administration of the last dose of drug. The apparatus yields a measure of changes in respiratory pattern known as enhanced Pause (Penh), which correlates with and can be used to monitor airway resistance (Hamelmann et al., 1997). Responses to methacholine (aerosolized from solutions of 3.125 to 50 mg/ml) were measured as described (Foster et al., 2000). We have demonstrated that in this chronic exposure model increased Penh correlates with increased specific airway resistance measured using a low-frequency forced oscillation technique (R. A. Collins, P. D. Sly, D. J. Turner, C. Herbert, and R. K. Kumar, submitted for publication).
Histomorphometry and Immunohistochemistry. The trachea and lungs were collected 18 h after the last inhalational exposure, fixed in 10% buffered formalin overnight, and embedded in paraffin. Although changes of inflammation and remodeling are demonstrable in the trachea, main bronchi, and intrapulmonary airways in this chronic exposure model, morphometric quantification of airway changes was performed in sections of the longitudinally oriented trachea for convenience of sampling and measurement. Numbers of eosinophils within the airway epithelial layer and of nuclear profiles in the lamina propria were counted in H&E-stained sections of the trachea. The thickness of the subepithelial zone of collagenization and of the epithelial layer were assessed in reticulin-stained sections. Mucus-secreting goblet cells were quantified in intrapulmonary airways in sections stained with Alcian Blue-PAS. The validity and reliability of the morphometric techniques we employed have been established in previous reports (Temelkovski et al., 1998; Foster et al., 2000; Kumar et al., 2002).
Immunohistochemical staining was performed as previously described (Kumar et al., 2002) with affinity-purified rabbit polyclonal primary antibodies to transforming growth factor-1 (TGF-1) (sc-146) or the RelA subunit of nuclear factor-B (NF-B) (sc-372) (Santa Cruz Biotechnology, Santa Cruz, California) and a peroxidase-anti-peroxidase detection system. For NF-B staining, antigen retrieval was performed by boiling deparaffinized sections in 0.01 M citrate buffer (pH 6.0) for 10 min in a microwave.
Because of the nonlinear relationship between amount of antigen and accumulation of immunoperoxidase reaction product, intensity of immunoreactivity was assessed semiquantitatively rather than by image analysis. Grading was performed by a single observer blinded to the identity of the samples and slides were presented in random order for examination. The scale used was 0 = no staining, 1 = weak staining, 2 = moderate staining, and 3 = strong staining.
Statistical Analysis. In general, one-way analysis of variance followed by Newman-Keuls multiple comparison test was used to examine differences between groups. Where grading was used for assessment, a nonparametric Kruskal-Wallis test followed by Dunn's test was employed. GraphPad Prism 3.03 (GraphPad Software, Inc., San Diego, California) was used for all data analysis.
|
Results |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
Airway Inflammation. We have previously shown that whereas eosinophils are rarely identifiable within the tracheal epithelium of normal BALB/c mice, sensitized mice exhibited recruitment of numerous intraepithelial eosinophils after long-term inhalation exposure to aerosolized ovalbumin (Temelkovski et al., 1998). This finding was reproduced in sensitized mice treated with vehicle alone (p < 0.001 compared with unexposed controls; Fig. 1A). Treatment with each of the three drugs tested led to a reduction in the accumulation of eosinophils (p < 0.001 compared with vehicle-treated controls for roflumilast, p < 0.01 for the other two drugs; Fig. 1A).
|
Sensitized chronically exposed BALB/c mice treated with vehicle alone developed widespread multifocal accumulation of lymphocytes, plasma cells and other chronic inflammatory cells in the lamina propria of the trachea (Fig. 2A) and the increase in cell numbers was similar to that previously described in untreated animals (p < 0.001 compared with unexposed controls; Fig. 1B). Accumulation of lamina propria cells was significantly diminished in mice treated with roflumilast (Fig. 2B) or dexamethasone (p < 0.01 for both compared with vehicle-treated controls; Fig. 1B) but was unaffected in mice treated with pentoxifylline.
|
Airway Wall Remodeling. As has previously been demonstrated in untreated animals (Temelkovski et al., 1998), sensitized mice exposed to antigen and treated with vehicle alone exhibited accumulation of subepithelial collagen (Fig. 3A), leading to significant thickening of the reticulin-stained zone (p < 0.001 compared with unexposed controls; Fig. 4A). In mice treated with roflumilast, the thickness of this zone was similar to that in unexposed controls (Fig. 3B), and the decrease in mean thickness was statistically significant (p < 0.001 compared with vehicle-treated controls; Fig. 4A). Dexamethasone also decreased the subepithelial accumulation of collagen but the effect was less marked (p < 0.05). There was no significant diminution of subepithelial fibrosis in mice treated with pentoxifylline (Fig. 4A). Treatment with each of the three drugs prevented the development of thickening of the airway epithelium that was observed in mice treated with vehicle alone (p < 0.001 compared with vehicle-treated controls; Fig. 4B).
|
|
Mucus-secreting goblet cells, which are virtually absent in the intrapulmonary airways of naive mice, were strikingly increased in sensitized exposed mice treated with vehicle only, with a median grade of 4. Treatment with roflumilast or pentoxifylline had little effect on the number of mucous cells, but there was a modest reduction in the proportion of goblet cells in the airways of dexamethasone-treated mice, which had a median grade of 3 (p < 0.05).
Airway Responsiveness. As reported previously for sensitized chronically exposed BALB/c mice (Foster et al., 2000), animals treated with vehicle exhibited a left-shifted Penh dose-response curve and increased maximal reactivity, characteristic of airway hyper-reactivity (Fig. 5). Animals treated with roflumilast or with dexamethasone exhibited a modest decrease in airway responsiveness, but this was not statistically significant. Animals treated with pentoxifylline demonstrated statistically significant reductions in Penh at methacholine concentrations of 6.25, 12.5, and 50 mg/ml (Fig. 5).
|
Immunohistochemistry. We have recently shown (R. K. Kumar, C. Herbert, and P. S. Foster, submitted for publication) that in sensitized BALB/c mice chronically exposed to inhaled antigen, there is a progressive increase in subepithelial immunoreactivity for TGF-1, which precedes but is spatially associated with collagen accumulation. To investigate possible mechanisms of inhibition of remodeling in drug-treated animals, we semiquantitatively assessed immunoreactivity for TGF-1. In vehicle-treated animals, subepithelial immunostaining was comparable to that previously observed in untreated mice and was significantly increased compared with naive animals (p < 0.001; Fig. 6A). The median grade of immunoreactivity was significantly diminished in dexamethasone-treated mice (p < 0.05 compared with vehicle-treated controls; Fig. 6A) but not in animals treated with the other drugs.
|
To investigate possible mechanisms of inhibition of inflammation in drug-treated animals, we semiquantitatively assessed expression of the RelA (p65) protein of the NF-B pathway. This revealed constitutive immunoreactivity in the cytoplasm of tracheal epithelial cells of naive mice (confirmed using another polyclonal antibody to p65; data not shown) and significant up-regulation of the intensity of immunoreactivity in sensitized BALB/c mice chronically exposed to inhaled antigen and treated with vehicle only (p < 0.05; Fig. 6B) but no evidence of nuclear immunoreactivity. Cytoplasmic immunostaining was markedly diminished in dexamethasone-treated mice, with a median grade lower than that in unexposed controls (p < 0.001 compared with vehicle-treated controls; Fig. 6B). Treatment with pentoxifylline reduced staining for p65 to the levels in unexposed control animals (p < 0.05 compared with vehicle-treated controls; Fig. 6B). Staining was also reduced in mice treated with roflumilast, but this effect did not achieve statistical significance.
|
Discussion |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
), to investigate inhibition of the airway lesions by PDE inhibitors compared with glucocorticoids. We have previously shown that in this model, changes of inflammation and airway wall remodeling are established by 4 weeks and progress with continuing exposure to antigen (Temelkovski et al., 1998). Therefore, we were able to assess whether these drugs could inhibit progression of or reverse these changes by treatment during weeks 5 and 6 of exposure.
Both roflumilast and dexamethasone were potent inhibitors of airway inflammation and remodeling. At the doses tested, the drugs suppressed the intraepithelial accumulation of eosinophils and the accumulation of chronic inflammatory cells in the lamina propria of the airways, as well as reversing subepithelial collagenization and epithelial hypertrophy. Inhibition of remodeling by inhaled glucocorticoids is well documented in human asthma (Hoshino et al., 1998b; Sont et al., 1999), and administration of glucocorticoids has also been shown to inhibit changes of airway fibrosis in other animal models (Blyth et al., 2000; Vanacker et al., 2001). However, our study demonstrates for the first time that comparable suppression of subepithelial fibrosis and epithelial hypertrophy can be achieved following treatment with a PDE4-selective inhibitor.
Although both roflumilast nor dexamethasone caused modest inhibition of airway responsiveness to methacholine in our model of chronic asthma, these effects were not statistically significant at the doses tested. The same dose of roflumilast is effective in inhibiting both antigen-induced bronchoconstriction and AHR in an acute allergen challenge model of asthmatic inflammation in rats (Bundschuh et al., 2001; Wollin et al., 2002), and a comparable dose of dexamethasone similarly decreases AHR to methacholine in acute models (Trifilieff et al., 2000). However, our studies in the chronic model of asthma using gene-targeted mice have clearly demonstrated that different mechanisms are involved in chronic AHR (Kumar and Foster, 2002). Given that the doses administered were chosen on the basis of anti-inflammatory activity, it is entirely possible that higher doses of these drugs would be able to significantly suppress AHR. This might be analogous to the need for higher doses of inhaled glucocorticoids to achieve effective control of AHR in human asthma (Sont et al., 1999).
In contrast to the inhibition of mucous cell hyperplasia/metaplasia by dexamethasone, which replicates previous observations in a murine model (Blyth et al., 1998), treatment with roflumilast did not suppress goblet cell change in this model. This result was in contrast to observations in an acute exposure model of asthmatic inflammation in which the PDE4-selective inhibitor rolipram was demonstrated to inhibit the goblet cell response (Kanehiro et al., 2001) and further highlights that phenotypically similar lesions may be differentially modified in acute and chronic disease.
The nonselective PDE inhibitor pentoxifylline had lesser effects on chronic airway inflammation and remodeling than either roflumilast or dexamethasone, being able to inhibit only eosinophil accumulation and epithelial thickening at the dose tested. Despite this, pentoxifylline significantly decreased AHR in this model of chronic asthma. We speculate that this could be related to the ability of this agent to suppress production of Th1 cytokines (Rott et al., 1993), among which interferon-
has been identified as possibly contributing to AHR (Fleming et al., 2001). Alternatively, pentoxifylline might act via a direct effect on airway smooth muscle as a consequence of inhibition of other PDE isoenzymes (Schmidt et al., 2000).
The mechanism of inhibition of remodeling by roflumilast and dexamethasone is unclear, although inhibition of growth factors for fibroblasts seems plausible. In human studies, treatment with inhaled glucocorticoids has been demonstrated to decrease expression of insulin-like growth factor-1 (Hoshino et al., 1998b). Epithelial cell-derived growth factors of the TGF- family are considered to be particularly important in the remodeling of the airways in asthma (Davies et al., 2003). We have recently shown (R. K. Kumar, C. Herbert, P. S. Foster, submitted for publication) that in sensitized BALB/c mice chronically exposed to inhaled antigen, there is a progressive increase in subepithelial immunoreactivity for TGF-1, which precedes the development of subepithelial fibrosis. Furthermore, interleukin-13-deficient mice and mice depleted of CD4+ T cells by chronic administration of a monoclonal antibody, in both of which remodeling was abrogated, failed to exhibit accumulation of TGF-1. We therefore investigated the relationship between inhibition of remodeling and expression of TGF-1 by immunohistochemistry. Interestingly, this revealed that whereas treatment with dexamethasone significantly decreased subepithelial immunoreactivity for TGF-1, roflumilast had no such effect. This result suggests that it might affect remodeling by mechanisms distinct from glucocorticoids, for example by a direct effect on fibroblast accumulation and function (Kohyama et al., 2002).
The NF-B pathway, which is a major signaling mechanism involved in regulation of the inflammatory response, is inhibited by glucocorticoids and PDE inhibitors (Almawi and Melemedjian, 2002; Haddad et al., 2002). Airway epithelial cell expression of the RelA subunit of NF-B is up-regulated following antigen challenge of sensitized animals (Poynter et al., 2002). We therefore investigated whether the activity of roflumilast or dexamethasone was related to inhibition of expression of this protein. Mice chronically exposed to inhaled antigen and treated with vehicle control exhibited enhanced epithelial cytoplasmic expression of RelA protein. Whereas treatment with dexamethasone strikingly diminished the intensity of immunoreactivity for RelA, the effect of pentoxifylline was less marked, while the effect of roflumilast did not achieve statistical significance. The difference between pentoxifylline and roflumilast might be attributed to the more effective inhibition of NF-B signaling by nonspecific PDE inhibitors than by PDE4-selective agents (Haddad et al., 2002).
In conclusion, we have demonstrated that in experimental chronic asthma, treatment with the novel PDE4-selective inhibitor roflumilast effectively inhibits both acute and chronic airway inflammation, as well as changes of remodeling. The mechanisms of the effects of roflumilast appear to differ from those of glucocorticoids. Our findings lend support to the notion that PDE4-selective inhibitors could be of value in the treatment of asthma, either as alternatives or as adjuncts to conventional glucocorticoid therapy.
|
Footnotes |
|---|
ABBREVIATIONS: AHR, airway hyper-reactivity; PDE, phosphodiesterase; Penh, enhanced Pause; TGF-1, transforming growth factor-1; NF-B, nuclear factor-B.
Address correspondence to: R. K. Kumar, Department of Pathology, University of New South Wales, Sydney, Australia 2052. E-mail: r.kumar{at}unsw.edu.au
|
References |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
Almawi WY and Melemedjian OK (2002) Negative regulation of nuclear factor-B activation and function by glucocorticoids. J Mol Endocrinol 28: 69–78.[Abstract]
Barsig J, Leung B, Bundschuh DS, Wollin L, Beume R, and Liew FY (2001) Protection by the phosphodiesterase-4 inhibitor roflumilast of mice against collagen-induced arthritis. Ann Rheum Dis 60: 156S.
Blyth DI, Pedrick MS, Savage TJ, Bright H, Beesley JE, and Sanjar S (1998) Induction, duration and resolution of airway goblet cell hyperplasia in a murine model of atopic asthma: effect of concurrent infection with respiratory syncytial virus and response to dexamethasone. Am J Respir Cell Mol Biol 19: 38–54.
Blyth DI, Wharton TF, Pedrick MS, Savage TJ, and Sanjar S (2000) Airway subepithelial fibrosis in a murine model of atopic asthma: suppression by dexamethasone or anti-interleukin-5 antibody. Am J Respir Cell Mol Biol 23: 241–246.
Bousquet J, Jeffery PK, Busse WW, Johnson M, and Vignola A (2000) Asthma: from bronchoconstriction to airways inflammation and remodeling. Am J Respir Crit Care Med 161: 1720–1745.
Bundschuh DS, Eltze M, Barsig J, Wollin L, Hatzelmann A, and Beume R (2001) In vivo efficacy in airway disease models of roflumilast, a novel orally active PDE4 inhibitor. J Pharmacol Exp Ther 297: 280–290.
Chetta A, Foresi A, Del Donno M, Consigli GF, Bertorelli G, Pesci A, Barbee RA, and Olivieri D (1996) Bronchial responsiveness to distilled water and methacholine and its relationship to inflammation and remodeling of the airways in asthma. Am J Respir Crit Care Med 153: 910–917.[Abstract]
Compton CH, Gubb J, Nieman R, Edelson J, Amit O, Bakst A, Ayres JG, Creemers JPHM, Schultze-Werninghaus G, Brambilla C, and Barnes NC (2001) Cilomilast, a selective phosphodiesterase-4i nhibitor for treatment of patients with chronic obstructive pulmonary disease: a randomised, dose-ranging study. Lancet 358: 265–270.[CrossRef][Medline]
Conti M, Richter W, Mehats C, Livera G, Park JY, and Jin C (2003) Cyclic AMP-specific PDE4 phosphodiesterases as critical components of cyclic AMP signaling. J Biol Chem 278: 5463–5496.
Davies DE, Wicks J, Powell RM, Puddicombe SM, and Holgate ST (2003) Airway remodeling in asthma: new insights. J Allergy Clin Immunol 111: 215–225.[CrossRef][Medline]
Fleming CM, He H, Ciota A, Perkins D, and Finn PW (2001) Administration of pentoxifylline during allergen sensitization dissociates pulmonary allergic inflammation from airway hyperresponsiveness. J Immunol 167: 1703–1711.
Foster PS, Ming Y, Matthei KI, Young IG, Temelkovski J, and Kumar RK (2000) Dissociation of inflammatory and epithelial responses in a murine model of chronic asthma. Lab Investig 80: 655–662.[Medline]
Haddad JJ, Land SC, Tarnow-Mordi WO, Zembala M, Kowalczyk D, and Lauterbach R (2002) Immunopharmacological potential of selective phosphodiesterase inhibition. II. Evidence for the involvement of an inhibitory-B/nuclear factor-B-sensitive pathway in alveolar epithelial cells. J Pharmacol Exp Ther 300: 567–576.
Hamelmann E, Schwarze J, Takeda K, Oshiba A, Larsen GL, Irvin CG, and Gelfand EW (1997) Noninvasive measurement of airway responsiveness in allergic mice using barometric plethysmography. Am J Respir Crit Care Med 156: 766–775.
Hatzelmann A and Schudt C (2001) Anti-inflammatory and immunomodulatory potential of the novel PDE4 inhibitor roflumilast in vitro. J Pharmacol Exp Ther 297: 267–279.
Hoshino M, Nakamura Y, Sim JJ, Shimojo J, and Isogai S (1998a) Bronchial subepithelial fibrosis and expression of matrix metalloproteinase-9 in asthmatic airway inflammation. J Allergy Clin Immunol 102: 783–788.[CrossRef][Medline]
Hoshino M, Nakamura Y, Sim JJ, Yamashiro Y, Uchida K, Hosaka K, and Isogai S (1998b) Inhaled corticosteroid reduced lamina reticularis of the basement membrane by modulation of insulin-like growth factor (IGF)-I expression in bronchial asthma. Clin Exp Allergy 28: 568–577.[CrossRef][Medline]
Houslay MD and Adams RD (2003) PDE4 cAMP phosphodiesterases: modular enzymes that orchestrate signalling cross-talk, desensitization and compartmentalization. Biochem J 370: 1–18.[CrossRef][Medline]
Howarth PH (2001) The influence of pharmacological therapy on airway remodeling in asthma, in Airway Remodeling (Howarth PH, Wilson JW, Bousquet J, Rak S, and Pauwels RA eds) pp 167–188, Marcel Dekker, New York.
Kanehiro A, Ikemura T, Makela MJ, Lahn M, Joetham A, Dakhama A, and Gelfand EW (2001) Inhibition of phosphodiesterase 4 attenuates airway hyperresponsiveness and airway inflammation in a model of secondary allergen challenge. Am J Respir Crit Care Med 163: 173–184.
Kohyama T, Liu X, Wen FQ, Zhu YK, Wang H, Kim HJ, Takizawa H, Cieslinski LB, Barnette MS, and Rennard SI (2002) PDE4 inhibitors attenuate fibroblast chemotaxis and contraction of native collagen gels. Am J Respir Cell Mol Biol 26: 694–701.
Kremsner PG, Grundmann H, Neifer S, Sliwa K, Sahlmuller G, Hegenscheid B, and Bienzle U (1991) Pentoxifylline prevents murine cerebral malaria. J Infect Dis 164: 605–608.[Medline]
Kumar RK (2001) Understanding airway wall remodeling in asthma: a basis for improvements in therapy? Pharmacol Ther 91: 93–104.[CrossRef][Medline]
Kumar RK and Foster PS (2002) Modeling allergic asthma in mice: pitfalls and opportunities. Am J Respir Cell Mol Biol 27: 267–272.
Kumar RK, Thomas PS, Seetoo DQ, Herbert C, McKenzie AN, Foster PS, and Lloyd AR (2002) Eotaxin expression by epithelial cells and plasma cells in chronic asthma. Lab Investig 82: 495–504.[CrossRef][Medline]
Niimi A, Matsumoto H, Amitani R, Nakano Y, Mishima M, Minakuchi M, Nishimura K, Itoh H, and Izumi T (2000) Airway wall thickness in asthma assessed by computed tomography: relation to clinical indices. Am J Respir Crit Care Med 162: 1518–1523.
Poynter ME, Irvin CG, and Janssen-Heininger YM (2002) Rapid activation of nuclear factor-B in airway epithelium in a murine model of allergic airway inflammation. Am J Pathol 160: 1325–1334.
Rott O, Cash E, and Fleischer B (1993) Phosphodiesterase inhibitor pentoxifylline, a selective suppressor of T helper type-1 but not type 2-associated lymphokine production, prevents induction of experimental autoimmune encephalomyelitis in Lewis rats. Eur J Immunol 23: 1745–1751.[Medline]
Schmidt DT, Watson N, Dent G, Ruhlmann E, Branscheid D, Magnussen H, and Rabe KF (2000) The effect of selective and non-selective phosphodiesterase inhibitors on allergen- and leukotriene C4-induced contractions in passively sensitized human airways. Br J Pharmacol 131: 1607–1618.[CrossRef][Medline]
Schudt C, Tenor H, and Hatzelmann A (1995) PDE isoenzymes as targets for anti-asthma drugs. Eur Respir J 8: 1179–1183.[Abstract]
Sont JK, Willems LNA, Bel EH, van Krieken HJM, Vendenbroucke JP, Sterk PJ, and the AMPUL Study Group (1999) Clinical control and histopathologic outcome of asthma when using airway hyperresponsiveness as an additional guide to long-term treatment. Am J Respir Crit Care Med 159: 1043–1051.
Souness JE, Houghton C, Sardar N, and Withnall MT (1999) Suppression of anti-CD3-induced interleukin-4 and interleukin-5 release from splenocytes of Mesocestoides corti-infected BALB/c mice by phosphodiesterase 4 inhibitors. Biochem Pharmacol 58: 991–999.[CrossRef][Medline]
Temelkovski J, Hogan SP, Shepherd DP, Foster PS, and Kumar RK (1998) An improved murine model of asthma: selective airway inflammation, epithelial lesions and increased methacholine responsiveness following chronic exposure to aerosolised allergen. Thorax 53: 849–856.
Timmer W, Leclerc V, Birraux G, Neuhauser M, Hatzelmann A, Bethke T, and Wurst W (2002) The new phosphodiesterase 4 inhibitor roflumilast is efficacious in exercise-induced asthma and leads to suppression of LPS-stimulated TNF- ex vivo. J Clin Pharmacol 42: 297–303.[Abstract]
Torphy TJ (1998) Phosphodiesterase isozymes: molecular targets for novel anti-asthma agents. Am J Respir Crit Care Med 157: 351–370.
Trifilieff A, El-Hashim A, and Bertrand C (2000) Time course of inflammatory and remodeling events in a murine model of asthma: effect of steroid treatment. Am J Physiol Lung Cell Mol Physiol 279: L1120–L1128.
Vanacker NJ, Palmans E, Kips JC, and Pauwels RA (2001) Fluticasone inhibits but does not reverse allergen-induced structural airway changes. Am J Respir Crit Care Med 163: 674–679.
Verghese MW, McConnell RT, Strickland AB, Gooding RC, Stimpson SA, Yarnall DP, Taylor JD, and Furdon PJ (1995) Differential regulation of human monocyte-derived TNF and IL-1 by type IV cAMP-phosphodiesterase (cAMP-PDE) inhibitors. J Pharmacol Exp Ther 272: 1313–1320.
Weston MC, Anderson N, and Peachell PT (1997) Effects of phosphodiesterase inhibitors on human lung mast cell and basophil function. Br J Pharmacol 121: 287–295.[CrossRef][Medline]
Wollin L, Barsig J, Bundschuh DS, Marx D, and Beume R (2002) PDE4-specific inhibition of airway hyperresponsiveness and pulmonary inflammation in rats: roflumilast versus rolipram, piclamilast and cilomilast. Am J Respir Crit Care Med 165: A311.
This article has been cited by other articles:
|
|
 |
|
  E. H. Walters, D. W. Reid, D. P. Johns, and C. Ward Nonpharmacological and pharmacological interventions to prevent or reduce airway remodelling Eur. Respir. J., September 1, 2007; 30(3): 574 - 588. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. W. J. Young, O. W. Williams, D. Chandra, L. K. Bellinghausen, G. Perez, A. Suarez, M. J. Tuvim, M. G. Roy, S. N. Alexander, S. J. Moghaddam, et al. Central Role of Muc5ac Expression in Mucous Metaplasia and Its Regulation by Conserved 5' Elements Am. J. Respir. Cell Mol. Biol., September 1, 2007; 37(3): 273 - 290. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. D. Bethke, G. M. Bohmer, R. Hermann, B. Hauns, R. Fux, K. Morike, M. David, D. Knoerzer, W. Wurst, and C. H. Gleiter Dose-Proportional Intraindividual Single- and Repeated-Dose Pharmacokinetics of Roflumilast, an Oral, Once-Daily Phosphodiesterase 4 Inhibitor J. Clin. Pharmacol., January 1, 2007; 47(1): 26 - 36. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Hauns, R. Hermann, A. Hunnemeyer, R. Herzog, D. Hauschke, K. Zech, and T. D. Bethke Investigation of a potential food effect on the pharmacokinetics of roflumilast, an oral, once-daily phosphodiesterase 4 inhibitor, in healthy subjects. J. Clin. Pharmacol., October 1, 2006; 46(10): 1146 - 1153. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Bergeron and L.-P. Boulet Structural changes in airway diseases: characteristics, mechanisms, consequences, and pharmacologic modulation. Chest, April 1, 2006; 129(4): 1068 - 1087. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 W. R. Henderson Jr., G. K. S. Chiang, Y.-t. Tien, and E. Y. Chi Reversal of Allergen-induced Airway Remodeling by CysLT1 Receptor Blockade Am. J. Respir. Crit. Care Med., April 1, 2006; 173(7): 718 - 728. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Lopez, V. del Pozo, T. Miguel, B. Sastre, C. Seoane, E. Civantos, E. Llanes, M. L. Baeza, P. Palomino, B. Cardaba, et al. Inhibition of Chronic Airway Inflammation and Remodeling by Galectin-3 Gene Therapy in a Murine Model J. Immunol., February 1, 2006; 176(3): 1943 - 1950. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H.-F. Tang, Y.-H. Song, J.-C. Chen, J.-Q. Chen, and P. Wang Upregulation of Phosphodiesterase-4 in the Lung of Allergic Rats Am. J. Respir. Crit. Care Med., April 15, 2005; 171(8): 823 - 828. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. K. Kumar, C. Herbert, D. C. Webb, L. Li, and P. S. Foster Effects of Anticytokine Therapy in a Mouse Model of Chronic Asthma Am. J. Respir. Crit. Care Med., November 15, 2004; 170(10): 1043 - 1048. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 |
 |
 |
|
 |
 |
 |
