Biomedical subjects

Clive P Page

Publications and source records attributed to Clive P Page.

At least 19 recordsLinked to original sources

PubMed2006

Activation of corticotropin-releasing factor receptor-2 causes bronchorelaxation and inhibits pulmonary inflammation in mice.

Urocortins are members of the corticotropin-releasing factor (CRF) family of peptides that bind to two receptors, CRF(1) and CRF(2). While CRF(1) is a high-affinity receptor for CRF, urocortin III binds with much greater affinity to CRF(2). In the present study we investigated the effect of CRF(2) receptor activation with urocortin III on airway smooth muscle tone in vitro and in an acute model of airway inflammation in mice. Urocortin III caused relaxation of methacholine-precontracted mouse tracheal segments. CRF caused similar relaxation, but with reduced potency compared to urocortin III, consistent with the CRF(2) receptor subtype. Relaxation induced by urocortin III was concentration-dependently inhibited by the CRF(2) antagonist, astressin 2B, with an IC(50) in the nanomolar range. These relaxations were potentiated by inhibition of phosphodiesterases but unaffected by inhibition of cyclooxygenase and NO or by removal of the epithelium. Finally, the number of neutrophils retrieved by bronchoalveolar lavage after administration of bacterial LPS (LPS) was reduced by prior intraperitoneal (i.p.) injection of urocortin III. This effect was also suppressed by astressin 2B, implicating CRF(2) receptors. Therefore, CRF(2) agonists appear to have both bronchorelaxant and anti-inflammatory activities and might represent an interesting therapeutic approach to the treatment of inflammatory lung diseases.

Animals↗

PubMed2006

Identification with MRI of the pleura as a major site of the acute inflammatory effects induced by ovalbumin and endotoxin challenge in the airways of the rat.

Inflammatory effects in the rat lung have been investigated, non-invasively by MRI, at early time points (3 and 6 h) after ovalbumin (OA) or endotoxin (LPS) challenges. Six hours after challenge with OA, a strong, even inflammatory signal was present around the periphery of the lung in a region corresponding to the pleura. Histological analysis confirmed the presence of marked edema associated with the pleural cavity of OA-treated animals. Lower levels of pleural edema were observed in MRI and histological evaluation of LPS-treated animals and no abnormality was observed in actively sensitized and naïve, saline-treated groups. Diffuse edematous signals were detected in the lung 3 and 6 h after challenge with OA or LPS; the signal volumes were larger at both time points following OA instillation. Bronchoalveolar lavage (BAL) fluid analysis performed 6 h after challenge revealed increased levels of protein and greater cellular activation in OA- than in LPS-treated animals. Furthermore, increased levels of peribronchial edema were found by histology 6 h after OA. BAL fluid and histological assessments demonstrated that the inflammatory signals were due to edema and not mucus as no significant changes in BAL mucin concentrations or differences in goblet cells were identified between OA or LPS challenge and their respective vehicle groups. Our data show that MRI is able to detect, non-invasively, inflammatory signals in both the lung and the pleura in spontaneously breathing animals, highlighting its potential to study the consequences of pulmonary insults on both sites.

Acute Disease↗

PubMed2006

Additional clinical benefit of enoxaparin in COPD patients receiving salmeterol and fluticasone propionate in combination.

It is now well recognised that heparin possesses numerous anti-inflammatory properties in addition to its anticoagulant properties. Thus, the aim of this study was to investigate the effects of the low molecular weight heparin, enoxaparin (ENX), as an add-on therapy for a period of 12 weeks, to inhaled salmeterol/fluticasone propionate (SLM/FP) combination in patients with stable chronic obstructive pulmonary disease (COPD). Forty-six patients were randomised to receive 12 weeks of treatment in one of two treatment groups: (1) fixed combination of SLM 50 microg and FP 500 microg Diskus, one inhalation twice daily; or (2) as group 1 plus 20 mg ENX administered subcutaneously once daily for 12 weeks. Patients attended the clinic before and after 4, 8 and 12 weeks of treatment for evaluations of lung function, blood gas tensions, dyspnoea and supplemental salbutamol use. Thirty-six patients completed the 12-week treatment period, 20 from group 1 and 16 from group 2. A significant increase in forced expiratory volume in 1 s (FEV1) over baseline was observed after 12 weeks of treatment in group 1 (0.145 L, 95% CI: 0.994-1.406, p<0.01), whilst significant increases in FEV1 over baseline were observed in group 2 after 4, 8 and 12 weeks of treatment with a maximum increase at 12 weeks of 0.244 L (95% CI: 1.175-1.596, p<0.01). Both treatment groups experienced similar improvements in blood gas tensions, dyspnoea and supplemental salbutamol use. Our results suggest that addition of ENX to conventional therapy of COPD may provide additional clinical benefit and must be further investigated as a treatment for COPD.

Aged↗

PubMed2006

Markers of exacerbation severity in chronic obstructive pulmonary disease.

BACKGROUND: Patients with chronic obstructive pulmonary disease (COPD) can experience 'exacerbations' of their conditions. An exacerbation is an event defined in terms of subjective descriptors or symptoms, namely dyspnoea, cough and sputum that worsen sufficiently to warrant a change in medical management. There is a need for reliable markers that reflect the pathological mechanisms that underlie exacerbation severity and that can be used as a surrogate to assess treatment effects in clinical studies. Little is known as to how existing study variables and suggested markers change in both the stable and exacerbation phases of COPD. In an attempt to find the best surrogates for exacerbations, we have reviewed the literature to identify which of these markers change in a consistent manner with the severity of the exacerbation event. METHODS: We have searched standard databases between 1966 to July 2004 using major keywords and terms. Studies that provided demographics, spirometry, potential markers, and clear eligibility criteria were included in this study. Central tendencies and dispersions for all the variables and markers reported and collected by us were first tabulated according to sample size and ATS/ERS 2004 Exacerbation Severity Levels I to III criteria. Due to the possible similarity of patients in Levels II and III, the data was also redefined into categories of exacerbations, namely out-patient (Level I) and in-patient (Levels II & III combined). For both approaches, we performed a fixed effect meta-analysis on each of the reported variables. RESULTS: We included a total of 268 studies reported between 1979 to July 2004. These studies investigated 142,407 patients with COPD. Arterial carbon dioxide tension and breathing rate were statistically different between all levels of exacerbation severity and between in out- and in-patient settings. Most other measures showed weak relationships with either level or setting, or they had insufficient data to permit meta-analysis. CONCLUSION: Arterial carbon dioxide and breathing rate varied in a consistent manner with exacerbation severity and patient setting. Many other measures showed weak correlations that should be further explored in future longitudinal studies or assessed using suggested mathematical modelling techniques.

Arteries↗

PubMed2006

The pharmacology of two novel long-acting phosphodiesterase 3/4 inhibitors, RPL554 [9,10-dimethoxy-2(2,4,6-trimethylphenylimino)-3-(n-carbamoyl-2-aminoethyl)-3,4,6,7-tetrahydro-2H-pyrimido[6,1-a]isoquinolin-4-one] and RPL565 [6,7-dihydro-2-(2,6-diisopropylphenoxy)-9,10-dimethoxy-4H-pyrimido[6,1-a]isoquinolin-4-one].

The pharmacology of two novel, trequinsin-like PDE3/4 inhibitors, RPL554 [9,10-dimethoxy-2(2,4,6-trimethylphenylimino)-3-(N-carbamoyl-2-aminoethyl)-3,4,6,7-tetrahydro-2H-pyrimido-[6,1-a]isoquinolin-4-one] and RPL565 [6,7-dihydro-2-(2,6-diisopropylphenoxy)-9,10-dimethoxy-4H-pyrimido[6,1-a]isoquinolin-4-one], has been investigated in a number of in vitro and in vivo assays. Electrical field stimulation-induced contraction of guinea pig superfused isolated tracheal preparations was significantly inhibited by RPL554 (10 microM) and RPL565 (10 microM) (percentage control; 93 +/- 1.2 and 84.4 +/- 2.7, respectively). Contractile responses were suppressed for up to 12 h after termination of superfusion with RPL554 demonstrating a long duration of action. RPL554 and RPL565 inhibited, in a concentration-dependent manner, lipopolysaccharide-induced tumor necrosis factor alpha release from human monocytes [IC50; 0.52 microM (0.38-0.69) and 0.25 microM (0.18-0.35), respectively] and proliferation of human mononuclear cells to phytohemagglutinin [IC50; 0.46 microM (0.24-0.9) and 2.90 microM (1.6-5.4), respectively]. The inhibitory effect of these drugs in vitro was translated into anti-inflammatory activity in vivo. RPL554 (10 mg/kg) and RPL565 (10 mg/kg) administered orally significantly inhibited eosinophil recruitment following antigen challenge in ovalbumin-sensitized guinea pigs. Likewise, inhalation of dry powder containing RPL554 by conscious guinea pigs (25% in micronized lactose) 1.5 h before antigen exposure significantly inhibited the recruitment of eosinophils to the airways. Exposure of conscious guinea pigs to inhalation of dry powder containing RPL554 (2.5%) and RPL565 (25%) in micronized lactose significantly inhibited histamine-induced plasma protein extravasation in the trachea and histamine-induced bronchoconstriction over a 5.5-h period. Thus, RPL554 and RPL565 are novel, long-acting PDE 3/4 inhibitors exhibiting a broad range of both bronchoprotective and anti-inflammatory activities.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2006

Are phosphodiesterase 4 inhibitors just more theophylline?

Theophylline has been relegated to a second- or even third-line therapy in the treatment of asthma and chronic obstructive pulmonary disease (COPD), behind glucocorticosteroids and beta2-agonists, although recent findings have suggested that theophylline possesses anti-inflammatory and immunomodulatory effects in addition to its well-recognized effects as a bronchodilator. In part, theophylline has fallen out of favor because of its adverse side-effect profile, and this has led to the search for more effective and safer drugs based on the knowledge that theophylline is orally active and that it is a nonselective phosphodiesterase (PDE) inhibitor. This has led to the development of selective PDE4 inhibitors, originally designed for depression, for the treatment of both COPD and asthma. Such drugs have shown clinical efficacy in the treatment of respiratory disease while having a considerably safer side-effect profile in comparison with theophylline, particularly because there are no reported drug interactions with PDE4 inhibitors, a feature that complicates the use of theophylline. In addition, it is also becoming increasingly apparent that theophylline is not working solely through PDE inhibition, as formerly assumed, and that this drug has other relevant pharmacologic activities that are likely to contribute to its efficacy, such as adenosine receptor antagonism and induction of histone deacetylase. Thus, the introduction of PDE4 inhibitors represents an entirely new class of drugs for the treatment of respiratory disease.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2006

Pulmonary biomarkers in chronic obstructive pulmonary disease.

There has been increasing interest in using pulmonary biomarkers to understand and monitor the inflammation in the respiratory tract of patients with chronic obstructive pulmonary disease (COPD). In this Pulmonary Perspective we discuss the merits of the various approaches by reviewing the current literature on pulmonary biomarkers in COPD and underscore the need for more systematic studies in the future. Bronchial biopsies and bronchoalveolar lavage provide valuable information about inflammatory cells and mediators, but are invasive, so that repeated measurements have to be very limited in assessing any interventions. Induced sputum has provided considerable information about the inflammatory process, including mediators and proteinases in COPD, but selectively samples proximal airways and may not closely reflect distal inflammatory processes. Exhaled gases and breath condensate are noninvasive procedures, so repeated measurements are possible, but for some assays the variability is relatively high. There is relatively little information about how any of these biomarkers relate to other clinical outcomes, such as progression of the disease, severity of disease, clinical subtypes, or response to therapy. More information is also needed about the variability in these measurements. In the future, pulmonary biomarkers may be useful in predicting disease progression, indicating disease instability, and in predicting response to current therapies and novel therapies, many of which are now in development.

Biomarkers↗

PubMed2006

Selection of a 2-azabicyclo[2.2.2]octane-based alpha4beta1 integrin antagonist as an inhaled anti-asthmatic agent.

The alpha4beta1 integrin, expressed on eosinophils and neutrophils, induces inflammation in the lung by facilitating cellular infiltration and activation. From a number of potent alpha4beta1 antagonists that we evaluated for safety and efficacy, 1 was selected as a lead candidate for anti-asthma therapy by the inhalation route. We devised an optimized stereoselective synthesis to facilitate the preparation of a sufficiently large quantity of 1 for assessment in vivo. Administration of 1 to allergen-sensitive sheep by inhalation blocked the late-phase response of asthma and abolished airway hyper-responsiveness at 24h following the antigen challenge. Additionally, the recruitment of inflammatory cells into the lungs was inhibited. Administration of 1 to ovalbumin-sensitized guinea pigs intraperitoneally blocked airway resistance and inhibited the recruitment of inflammatory cells.

Administration, Inhalation↗

PubMed2006

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.

Animals↗

PubMed2006

Phosphodiesterase inhibitors.

Phosphodiesterases are a diverse family of enzymes that hydrolyse cyclic nucleotides and thus play a key role in regulating intracellular levels of the second messengers cAMP and cGMP, and hence cell function. Theophylline and papaverine have historically been used therapeutically and are known to be weak inhibitors of PDE, but to what extent this contributed toward their clinical efficacy was poorly defined. However, the discovery of 11 isoenzyme families and our increased understanding of their function at the cell and molecular level provides an impetus for the development of isoenzyme selective inhibitors for the treatment of various diseases. This review focuses on the development of PDE3 inhibitors for congestive heart failure, PDE4 inhibitors for inflammatory airways disease and most successfully, PDE5 inhibitors for erectile dysfunction.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2006

Roflumilast: a phosphodiesterase-4 inhibitor for the treatment of respiratory disease.

Asthma and chronic obstructive pulmonary disease (COPD) are two of the most common chronic diseases worldwide, yet the classes of drug licensed to treat these conditions have not changed appreciably over the last 20 years. Inhaled bronchodilators and glucocorticosteroids (often in combination) form the mainstay of therapy for respiratory diseases, but many patients (including the elderly and children) can have problems using inhaler devices and there is a clear preference for oral therapy. The prevalence of these respiratory diseases is on the increase worldwide and continues to represent an area of medicine with unmet medical needs, particularly in the treatment of COPD. Despite this increase, very few new classes of drugs have been introduced into clinical practice. Phosphodiesterase-4 inhibitors are a novel class of drugs in development for the treatment of respiratory diseases and there are a number of lead compounds in late clinical development. This review focuses on one of the most promising drugs in development, roflumilast, which has undergone extensive clinical evaluation.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2005

Markers of disease severity in chronic obstructive pulmonary disease.

BACKGROUND AND OBJECTIVES: Diagnosis and assessment of treatment effect in chronic obstructive pulmonary disease (COPD) have relied primarily on the examination of a complex set of symptoms and the use of spirometry. However, these methods require long periods of assessment to determine whether patients show clinically relevant improvements after intervention. We therefore wanted to determine how existing clinical and laboratory measures change with COPD severity and identify disease markers that can serve as better endpoints for diagnosis and assessment of COPD progression and treatment effect. METHODS: Using standard COPD keywords and terms, we searched PubMed, ISI Web of Science, and Cochrane Review databases for retrospective and prospective clinical studies published since 1966. We identified 652 studies (n = 146,255) from 1978 to September 2003 based on the availability of spirometric and demographic data, investigation of possible markers, absence of acute exacerbations and co-morbidities, and the withdrawal of standard COPD medication. Central tendencies and dispersions of subject baseline measures were collected according to study sample size, smoking status, and mild, moderate and severe COPD stages. A fixed effect meta-analysis was then conducted on each measure at various disease stages. RESULTS: Arterial oxygen tension, sputum neutrophils and IL-8, and serum TNF-alpha and C-Reactive Protein showed a trend toward separation between COPD stages. Other measures such as pack-years and St George's Respiratory Questionnaire only distinguished between disease and disease-free states. CONCLUSIONS: We observed little separation between disease stages for many measures used in COPD diagnosis and clinical trials. This demonstrates the poor sensitivity of such endpoints to define a patient's clinical status and to quantify treatment effect. Therefore, we recommend that longitudinal studies and disease modelling be the primary methods for assessing whether potential markers of disease progression can be used for COPD diagnosis and clinical trials.

Biomarkers↗

PubMed2005

Immunohistochemical localization of vanilloid receptor subtype 1 (TRPV1) in the guinea pig respiratory system.

Transient receptor potential vanilloid-1 (TRPV1) containing nerves are implicated in cough and bronchoconstriction although the significance of their documentation on non-neuronal cells is unclear. We have investigated the anatomical distribution and location of TRPV1 in an animal species often utilized in models of cough and airway inflammation. The distribution and localization of TRPV1 immunoreactivity in the lung was studied using confocal microscopy. Double labelling were carried out using the panaxonal marker, protein gene product 9.5 (PGP) and the neuropeptide substance P. TRPV1 was localized to fine axons within the epithelium of the trachea, however this represented only a fraction of the total axonal innervation of the epithelium. TRPV1 immunoreactive axons were also found in and around subepithelial regions of the airways, including smooth muscle and blood vessels and within the lower airways, found in the vicinity of bronchi and bronchioles, and in and around alveolar tissue. TRPV1 in the epithelium of the trachea was co-localized with substance P containing axons, although TRPV1 immunoreactive neuropeptide negative axons were also discernible. We found evidence for TRPV1 localization to axons throughout the respiratory tract. The distribution was heterogeneous and represented a fraction of the total neuronal innervation of the airways. No TRPV1 was found localized to airway epithelial cells. TRPV1 was often co-localized with the sensory neuropeptide substance P but there was evidence of TRPV1 positive neurones that did not express substance P. This suggests a role for TRPV1 in the airway that is independent of sensory neuropeptides.

Animals↗

PubMed2005

Pharmacological characterisation of the adenosine receptor mediating increased ion transport in the mouse isolated trachea and the effect of allergen challenge.

The effect of adenosine on transepithelial ion transport was investigated in isolated preparations of murine trachea mounted in Ussing chambers. The possible regulation of adenosine receptors in an established model of allergic airway inflammation was also investigated. Mucosally applied adenosine caused increases in short-circuit current (I(SC)) that corresponded to approximately 50% of the response to the most efficacious secretogogue, ATP (delta I(SC) 69.5 +/- 6.7 microA cm2). In contrast, submucosally applied adenosine caused only small (<20%) increases in I(SC), which were not investigated further. The A1-selective (N6-cyclopentyladenosine, CPA, 1 nM-10 microM), A2A-selective (2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxoamido adenosine; CGS 21680; 0.1-100 microM) and A3-selective (1-deoxy-1-[6-[[(3-iodophenyl)-methyl]amino]-9H-purin-9-yl]-N-methyl-beta-D-ribofuranuronamide; IB-MECA; 30 nM-100 microM) adenosine receptor agonists were either equipotent or less potent than adenosine, suggesting that these receptors do not mediate the response to adenosine. The A1 receptor selective antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX; 10 nM-1 microM) caused a rightward shift of the adenosine concentration-effect curve only at 1 microM. The mixed A2A/A2B receptor antagonist 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol (ZM 241385) also caused rightward shift of the adenosine concentration-effect curve, again only at micromolar concentrations, suggestive of the involvement of A2B receptors. In preparations from animals sensitised to ovalbumin and challenged over 3 days with aerosol ovalbumin, a decrease in baseline I(SC) was observed and responses to ATP were diminished. Similarly, the amplitude of responses to adenosine were attenuated although there was no change in potency. These results suggest that the A2B receptor mediates the I(SC) response to adenosine in the mouse trachea. This receptor does not appear to be regulated in a standard asthma model.

Adenosine↗

PubMed2005

Some structural determinants of the antiproliferative effect of heparin-like molecules on human airway smooth muscle.

Accumulation of airway smooth muscle (ASM) and its infiltration by mast cells are key pathological features of airway remodelling in asthma. Heparin, a major component of mast cell granules, inhibits ASM proliferation by an unknown mechanism. Here, unfractionated heparins and related glycosaminoglycans having structurally heterogeneous polysaccharide side chains that varied in molecular weight, sulphation and anionic charge were used to identify features of the heparin molecule that were required for its antiproliferative activity in cultured human ASM cells. Proliferation induced by 10% fetal bovine serum (FBS) was abrogated by two unfractionated commercial heparin preparations (Sigma and Multiparin) and this effect was reproduced with each of three low-molecular weight heparin preparations (3, 5 and 6 kDa, respectively), demonstrating that antiproliferative activity resided in at least a 3 kDa heparin fraction. N-desulphated 20% re-acetylated (N-de) heparin (anticoagulant) and O-desulphated heparin (O-de) (non-anticoagulant) fractions also inhibited FBS-dependent proliferation (rank potency: Sigma heparin > O-de > N-de) suggesting that the antiproliferative action of heparin involved N-sulphation but was independent of its anticoagulant activity. Other sulphated molecules with variable anionic charge (dextran sulphate, fucoidan, chondroitin sulphates A or B, heparan sulphate) inhibited proliferation to varying degrees, as did the non-sulphated molecules hyaluronic acid and poly-L-glutamic acid. However, nonsulphated dextran had no effect. In summary, attenuation of FBS-dependent proliferation of human ASM by heparin involves but does not depend upon sulphation, although loss of N-sulphation reduces antiproliferative activity. This antiproliferative effect is independent of anionic charge and the anticoagulant actions of heparin.

Adult↗

PubMed2004

The effect of selective phosphodiesterase isoenzyme inhibition on neutrophil function in vitro.

Neutrophil-derived proteases such as neutrophil elastase (NE) and matrix metalloproteinase (MMP) are implicated in the pathogenesis of Chronic Obstructive Pulmonary Disease (COPD). In this study, the effects of selective phosphodiesterase (PDE) inhibition on NE and MMP-9 release, as well as Myeloperoxidase (MPO) activity and integrin-mediated neutrophil adhesion to human umbilical vein endothelial cells (HUVECs), were investigated. Human neutrophils were treated with PDE inhibitors (10(-11)-10(-4)M) in the absence and presence of TNF-alpha (tumour necrosis factor) (100 U ml(-1)) for 30 min, prior to fMLP activation. After 45 min, the cells were removed and NE, MPO and MMP-9 release assessed. In the adhesion studies, the neutrophils were radio-labelled with 51Cr, stimulated and immediately transferred to cultured HUVEC monolayers for 30 min, prior to assessment of adhesion. TNF-alpha (100 U ml(-1)) acted synergistically with fMLP in stimulating azurophil degranulation with respect to both MPO activity (P<0.01) and NE release (P<0.01). In contrast, an additive effect was observed with TNF-alpha and fMLP with regard to MMP-9 release and neutrophil adhesion to HUVECs. The PDE4 inhibitors, roflumilast, roflumilast N-oxide, cilomilast and rolipram significantly suppressed MPO, NE and MMP-9 release in both the presence and absence of TNF-alpha (P<0.05; n=6-10) and also reduced neutrophil adhesion to HUVECs. In contrast, milrinone, a PDE3 inhibitor and the non-selective PDE inhibitor, theophylline did not inhibit azurophil degranulation under any of the experimental conditions. These data provide further evidence that selective PDE4 isoenzyme inhibitors can inhibit neutrophil degranulation, effects not shared by PDE3 inhibitors or theophylline.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2004

Platelet P-selectin is required for pulmonary eosinophil and lymphocyte recruitment in a murine model of allergic inflammation.

Platelets are necessary for lung leukocyte recruitment in a murine model of allergic inflammation, and platelet-leukocyte aggregates are formed in circulating blood of patients with asthma after allergen exposure. However, it is unknown how platelets induce pulmonary leukocyte recruitment in asthma. Here, we have investigated the importance of platelet adhesion molecule expression on pulmonary eosinophil and lymphocyte recruitment and on leukocyte CD11b and very late antigen (VLA)-4 expression in mice. Pulmonary leukocyte recruitment in platelet-depleted mice (sensitized and exposed to ovalbumin) transfused with fixed, unstimulated platelets (FUSPs) was abolished, whereas transfusion with platelets stimulated and fixed (FSPs), expressing P-selectin and P-selectin glycoprotein ligand-1 (PSGL-1), restored eosinophil and lymphocyte recruitment. Transfusion with platelets from P-selectin-deficient mice, or with FSPs stimulated in the presence of a blocking anti-P-selectin antibody, were unable to restore pulmonary leukocyte recruitment. Flow cytometric analysis revealed increased expression of CD11b and VLA-4 on leukocytes attached to platelets after allergen exposure, and CD11b expression on leukocytes was suppressed in thrombocytopenic mice but was restored with the transfusion of FSPs, but not FUSPs, a phenomenon concurrent with the formation of platelet-leukocyte complexes. P-selectin expression on the surfaces of platelets is a major requirement for pulmonary eosinophil and lymphocyte recruitment, allowing circulating platelets to bind to and stimulate leukocytes for endothelial attachment.

Animals↗

PubMed2004

Effects of inhaled thrombin receptor agonists in mice.

Active thrombin is found in the airways of patients with a variety of inflammatory lung diseases. However, whether thrombin contributes to the pathologies of these diseases is unknown, although thrombin is a potent inflammatory mediator in other organ systems. In the present study we have assessed the acute inflammatory effect of inhaled thrombin and investigated the possible receptors mediating any effects in mice. Thrombin (200-2000 U kg(-1) intranasally), induced the recruitment of a small, but significant, number of neutrophils into the airways as assessed by differential counts of cells retrieved by bronchoalveolar lavage (BAL). This small response was mimicked by peptide agonists of proteinase-activated receptor-4 (PAR(4); GYPGKF, AYPGKF; 2-20 mg kg(-1)), but not PAR(1) (SFLLRN; 2-20 mg kg(-1)). By contrast, trypsin (200-2000 U kg(-1)) caused profound inflammation and lung damage. Concentrations of tumour necrosis factor-alpha (TNF-alpha) were elevated in BAL fluid from thrombin-treated mice, and a TNF-alpha-neutralising antibody inhibited the influx of neutrophils in response to thrombin. Although isolated alveolar macrophages appeared to express PAR(1)- and PAR(4)-immunoreactivity, these cells failed to release TNF-alpha above baseline levels in response to thrombin, trypsin or any of the peptide PAR agonists. Neither thrombin (2000 U kg(-1)) nor trypsin (200 U kg(-1)) modified the airway neutrophilia in response to intranasal bacterial lipopolysaccharide (LPS; 100 micrograms kg(-1)). In conclusion, exogenous thrombin has only a modest acute inflammatory action in the lung that appears to be mediated by PAR(4) and involve release of TNF-alpha from an unknown source.

Administration, Inhalation↗