The Concise Guide to PHARMACOLOGY 2023/24: G protein-coupled receptors

The Concise Guide to PHARMACOLOGY 2023/24 is the sixth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of approximately 1800 drug targets, and about 6000 interactions with about 3900 ligands. There is an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (https://www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes almost 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/bph.16177. G protein-coupled receptors are one of the six major pharmacological targets into which the Guide is divided, with the others being: ion channels, nuclear hormone receptors, catalytic receptors, enzymes and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid-2023, and supersedes data presented in the 2021/22, 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC-IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.

Investigating Partially Discordant Results in Phase 3 Studies of Aducanumab

OBJECTIVES

Efficacy and safety results from the EMERGE (NCT02484547) and ENGAGE (NCT02477800) phase 3 studies of aducanumab in early Alzheimer's disease (AD) have been published. In EMERGE, but not in ENGAGE, high-dose aducanumab demonstrated significant treatment effects across primary and secondary endpoints. Low-dose aducanumab results were consistent across studies with non-significant differences versus placebo that were intermediate to the high-dose arm in EMERGE. The present investigation examined data from EMERGE and ENGAGE through post-hoc analyses to determine factors that contributed to discordant results between the high-dose arms of the two studies.

DESIGN

EMERGE and ENGAGE were 2 phase 3, randomized, double-blind, placebo-controlled, parallel-group studies.

SETTING

EMERGE and ENGAGE were 2 global multicenter studies involving 348 sites in 20 countries.

PARTICIPANTS

Participants in EMERGE and ENGAGE were aged 50 to 85 years and had mild cognitive impairment or mild AD dementia with confirmed amyloid pathology. The randomized and dosed population (all randomized patients who received at least one dose of study treatment) included 1638 patients in EMERGE and 1647 in ENGAGE.

INTERVENTION

In EMERGE and ENGAGE, participants were randomized to receive low- or high-dose aducanumab or placebo (1:1:1) once every 4 weeks.

MEASUREMENTS

In this paper, 4 areas were investigated through post-hoc analyses to understand the discordance in the high-dose arms of the EMERGE and ENGAGE studies: baseline characteristics, amyloid-related imaging abnormalities, non-normality of the data, and dosing/exposure to aducanumab.

RESULTS

Post-hoc analyses showed that outcomes in the ENGAGE high-dose group were affected by an imbalance in a small number of patients with extremely rapid progression and by lower exposure to the target dose of 10 mg/kg. These factors were confounded and present in early enrolled patients but were not present in later-enrolled patients who were randomized to the target dosing regimen of 10 mg/kg after titration. Neither baseline characteristics nor amyloid-related imaging abnormalities contributed to the difference in results between the high-dose arms.

CONCLUSIONS

Results were consistent across studies in later enrolled patients in which the incidence of rapidly progressing patients was balanced across treatment arms.

Two Randomized Phase 3 Studies of Aducanumab in Early Alzheimer's Disease

BACKGROUND

Alzheimer's disease is a progressive, irreversible, and fatal disease for which accumulation of amyloid beta is thought to play a key role in pathogenesis. Aducanumab is a human monoclonal antibody directed against aggregated soluble and insoluble forms of amyloid beta.

OBJECTIVES

We evaluated the efficacy and safety of aducanumab in early Alzheimer's disease.

DESIGN

EMERGE and ENGAGE were two randomized, double-blind, placebo-controlled, global, phase 3 studies of aducanumab in patients with early Alzheimer's disease.

SETTING

These studies involved 348 sites in 20 countries.

PARTICIPANTS

Participants included 1638 (EMERGE) and 1647 (ENGAGE) patients (aged 50-85 years, confirmed amyloid pathology) who met clinical criteria for mild cognitive impairment due to Alzheimer's disease or mild Alzheimer's disease dementia, of which 1812 (55.2%) completed the study.

INTERVENTION

Participants were randomly assigned 1:1:1 to receive aducanumab low dose (3 or 6 mg/kg target dose), high dose (10 mg/kg target dose), or placebo via IV infusion once every 4 weeks over 76 weeks.

MEASUREMENTS

The primary outcome measure was change from baseline to week 78 on the Clinical Dementia Rating Sum of Boxes (CDR-SB), an integrated scale that assesses both function and cognition. Other measures included safety assessments; secondary and tertiary clinical outcomes that assessed cognition, function, and behavior; and biomarker endpoints.

RESULTS

EMERGE and ENGAGE were halted based on futility analysis of data pooled from the first approximately 50% of enrolled patients; subsequent efficacy analyses included data from a larger data set collected up to futility declaration and followed prespecified statistical analyses. The primary endpoint was met in EMERGE (difference of -0.39 for high-dose aducanumab vs placebo [95% CI, -0.69 to -0.09; P=.012; 22% decrease]) but not in ENGAGE (difference of 0.03, [95% CI, -0.26 to 0.33; P=.833; 2% increase]). Results of biomarker substudies confirmed target engagement and dose-dependent reduction in markers of Alzheimer's disease pathophysiology. The most common adverse event was amyloid-related imaging abnormalities-edema.

CONCLUSIONS

Data from EMERGE demonstrated a statistically significant change across all four primary and secondary clinical endpoints. ENGAGE did not meet its primary or secondary endpoints. A dose- and time-dependent reduction in pathophysiological markers of Alzheimer's disease was observed in both trials.

THE CONCISE GUIDE TO PHARMACOLOGY 2021/22: G protein-coupled receptors

The Concise Guide to PHARMACOLOGY 2021/22 is the fifth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of nearly 1900 human drug targets with an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes over 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/bph.15538. G protein-coupled receptors are one of the six major pharmacological targets into which the Guide is divided, with the others being: ion channels, nuclear hormone receptors, catalytic receptors, enzymes and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid-2021, and supersedes data presented in the 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC-IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.

THE CONCISE GUIDE TO PHARMACOLOGY 2021/22: G protein-coupled receptors

The Concise Guide to PHARMACOLOGY 2021/22 is the fifth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of nearly 1900 human drug targets with an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes over 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/bph.15538. G protein-coupled receptors are one of the six major pharmacological targets into which the Guide is divided, with the others being: ion channels, nuclear hormone receptors, catalytic receptors, enzymes and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid-2021, and supersedes data presented in the 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC-IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.

Quantifying Beta-Galactosylceramide Kinetics in Cerebrospinal Fluid of Healthy Subjects Using Deuterium Labeling

Therapeutics promoting myelin synthesis may enhance recovery in demyelinating diseases, such as multiple sclerosis. However, no suitable method exists to quantify myelination. The turnover of galactosylceramide (myelin component) is indicative of myelination in mice, but its turnover has not been determined in humans. Here, six healthy subjects consumed 120 mL 70% D₂O daily for 70 days to label galactosylceramide. We then used mass spectrometry and compartmental modeling to quantify the turnover rate of galactosylceramide in cerebrospinal fluid. Maximum deuterium enrichment of body water ranged from 1.5–3.9%, whereas that of galactosylceramide was much lower: 0.05–0.14%. This suggests a slow turnover rate, which was confirmed by the model‐estimated galactosylceramide turnover rate of 0.00168 day⁻¹, which corresponds to a half‐life of 413 days. Additional studies in patients with multiple sclerosis are needed to investigate whether galactosylceramide turnover could be used as an outcome measure in clinical trials with remyelination therapies.

Evidence regarding the utility of multiple mini-interview (MMI) for selection to undergraduate health programs: A BEME systematic review: BEME Guide No. 37

BACKGROUND

In the 11 years since its development at McMaster University Medical School, the multiple mini-interview (MMI) has become a popular selection tool. We aimed to systematically explore, analyze and synthesize the evidence regarding MMIs for selection to undergraduate health programs.

METHODS

The review protocol was peer-reviewed and prospectively registered with the Best Evidence Medical Education (BEME) collaboration. Thirteen databases were searched through 34 terms and their Boolean combinations. Seven key journals were hand-searched since 2004. The reference sections of all included studies were screened. Studies meeting the inclusion criteria were coded independently by two reviewers using a modified BEME coding sheet. Extracted data were synthesized through narrative synthesis.

RESULTS

A total of 4338 citations were identified and screened, resulting in 41 papers that met inclusion criteria. Thirty-two studies report data for selection to medicine, six for dentistry, three for veterinary medicine, one for pharmacy, one for nursing, one for rehabilitation, and one for health science. Five studies investigated selection to more than one profession. MMIs used for selection to undergraduate health programs appear to have reasonable feasibility, acceptability, validity, and reliability. Reliability is optimized by including 7-12 stations, each with one examiner. The evidence is stronger for face validity, with more research needed to explore content validity and predictive validity. In published studies, MMIs do not appear biased against applicants on the basis of age, gender, or socio-economic status. However, applicants of certain ethnic and social backgrounds did less well in a very small number of published studies. Performance on MMIs does not correlate strongly with other measures of noncognitive attributes, such as personality inventories and measures of emotional intelligence.

DISCUSSION

MMI does not automatically mean a more reliable selection process but it can do, if carefully designed. Effective MMIs require careful identification of the noncognitive attributes sought by the program and institution. Attention needs to be given to the number of stations, the blueprint and examiner training.

CONCLUSION

More work is required on MMIs as they may disadvantage groups of certain ethnic or social backgrounds. There is a compelling argument for multi-institutional studies to investigate areas such as the relationship of MMI content to curriculum domains, graduate outcomes, and social missions; relationships of applicants' performance on different MMIs; bias in selecting applicants of minority groups; and the long-term outcomes appropriate for studies of predictive validity.

The Concise Guide to PHARMACOLOGY 2013/14: overview

The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties from the IUPHAR database. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. This compilation of the major pharmacological targets is divided into seven areas of focus: G protein-coupled receptors, ligand-gated ion channels, ion channels, catalytic receptors, nuclear hormone receptors, transporters and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors & Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and GRAC and provides a permanent, citable, point-in-time record that will survive database updates.

Eosinophil chemotaxis

Chemotaxis assays have a number of applications in the study of leukocyte biology and immune/inflammatory pathology. Multiwell "blind chamber"-type assays allow a large number of parallel measurements within a single assay. The development of fluorescence assays using microplate-based chemotaxis chambers has permitted a degree of automation to be applied to these assays. Here, a method is described for the quantitative measurement of eosinophil migration using a 96-well assay with numbers of cells that may realistically be obtained from blood samples.

Prosurvival activity for airway neutrophils in severe asthma

BACKGROUND

Airway neutrophilia is a recognised feature of chronic severe asthma, but the mechanisms that underlie this phenomenon are unknown. Evidence for factors present in airway secretions that prolong neutrophil survival has been sought and it has been hypothesised that these might be augmented in neutrophilic asthma.

METHODS

Non-smoking subjects with severe asthma (SA) or mild asthma (MA) and healthy control subjects (HC) underwent sputum induction. The SA group was subdivided into subjects with neutrophil counts above (SA-high) and those within the normal range (SA-low). Apoptotic neutrophils were enumerated in the cellular phase while the fluid phase was assessed for its ability to prolong the in vitro survival of blood-derived neutrophils using morphometric and flow cytometric analyses.

RESULTS

There was a significant difference between all four subject groups with respect to the percentage of apoptotic sputum neutrophils (Kruskal-Wallis, p=0.042). Cuzick test showed a highly significant (p=0.008) trend towards decreasing numbers of apoptotic neutrophils across the four groups with increasing asthma severity and neutrophil count. The sputum antiapoptotic activity was also different between the groups (p=0.039), with a highly significant (p=0.005) decreasing trend across the four groups. The survival effect could not be inhibited by blocking selective chemotaxin receptors, neutralising neutrophil survival factors, inhibiting phosphatidylinositol-3-kinase (using LY294002) or with pertussis toxin pretreatment. Similarly, it could not be explained by lipopolysaccharide contamination or by the presence of inhaled corticosteroids in sputum.

CONCLUSIONS

These data demonstrate the capacity of as yet unidentified factor(s) in the airways of subjects with asthma to delay human neutrophil apoptosis and extend their lifespan as a potential mechanism contributing to unresolving airways neutrophilia in severe asthma.

Impaired neutrophil chemotaxis in chronic obstructive pulmonary disease

RATIONALE

Neutrophilic airway inflammation is considered to be a major factor in the pathogenesis of chronic obstructive pulmonary disease (COPD), with sputum and bronchoalveolar lavage neutrophil counts broadly correlating with disease severity. The mechanisms responsible for neutrophil accumulation are poorly understood, but they could involve increased influx and/or survival of these cells.

OBJECTIVES

To investigate whether neutrophil chemotactic responsiveness and/or chemotactic activity in airway secretions are increased in subjects with COPD.

METHODS

Chemotaxis experiments were performed using induced sputum supernatants from subjects with and without COPD as a source of chemotactic activity, and neutrophils from healthy donors as responder cells. In addition, chemotactic responses to N-formyl-Met-Leu-Phe (fMLP) and interleukin-8 (IL-8/CXCL8) were studied using neutrophils from healthy subjects and subjects with COPD.

MEASUREMENTS AND MAIN RESULTS

As reported in the literature, sputum neutrophil counts were significantly increased in subjects with COPD compared with healthy subjects. However, this was associated with reduced chemotactic activity in sputum in COPD, as judged by reduced chemotaxis to the fluid phase of sputum from subjects with COPD compared with healthy subjects. Furthermore, whereas neutrophils from subjects with stage I COPD had normal responses to fMLP and IL-8, subjects with more severe stage II-IV COPD showed reduced levels of spontaneous migration and chemotaxis to fMLP and IL-8.

CONCLUSIONS

Neither increased chemotactic activity in the airways nor increased chemotactic responsiveness of neutrophils explains the increased number of these cells in subjects with stable COPD. The implications of the observed reduction in neutrophil chemotactic activity remain to be established.

Differential dependence of eosinophil chemotactic responses on phosphoinositide 3-kinase (PI3K)

BACKGROUND

Control of eosinophil migration to sites of inflammatory responses is a potentially therapeutic intervention in diseases such as bronchial asthma. Chemoattractants, their receptors and the associated signalling pathways may, therefore, be important targets for novel therapeutics. While several potentially important chemoattractants have been identified, the signalling pathways mediating their actions are incompletely understood.

AIMS OF THE STUDY

The role of phosphoinositide 3-kinase (PI3K) in responses of human eosinophils to two important eosinophil chemoattractants -- platelet-activating factor (PAF) and eotaxin (CCL11) -- was studied to determine whether this enzyme activity might be crucial for eosinophil migration.

METHODS

Eosinophils were isolated from atopic donor blood by immunomagnetic selection. Chemotaxis was assayed in a 96-well blind-chamber cell fluorescence assay. Respiratory burst and leukotriene C(4) secretion were also assayed.

RESULTS

Two PI3K inhibitors, wortmannin and LY294002, caused concentration-dependent inhibition of PAF-induced eosinophil chemotaxis (IC(50) = 0.54 nM and 0.15 microM, respectively) but exhibited at least 100-fold lower potency against eotaxin-induced responses (IC(50) = 48 nM and >100 microM, respectively), indicating that these responses were not dependent upon PI3K. Wortmannin and LY294002 also inhibited PAF induced respiratory burst but not PAF-induced LTC(4) secretion.

CONCLUSIONS

We conclude that PI3K-dependence varies with stimulus and response, and that eotaxin-induced eosinophil migration is not controlled by PI3K. This may indicate a limit to the potential of PI3K inhibitors to suppress tissue eosinophilia in diseases such as asthma.

Linking solution chemistry to crystal nucleation: the case of tetrolic acid

The application of FTIR spectroscopy to concentrated solutions of tetrolic acid shows, for the first time, a direct relationship between molecular self association in solution and H-bonded motifs in the subsequently crystallised solid phases.

Measurement of eotaxin (CCL11) in induced sputum supernatants: validation and detection in asthma

BACKGROUND

Induced sputum is widely used in asthma research; however, for many mediators, the detection methods have not been validated.

OBJECTIVE

We sought to optimize the method of detection of eotaxin, an important chemokine acting through the CCR3 receptor on eosinophils, basophils, and T(H)2 cells.

METHODS

Induced sputum from normal and asthmatic subjects was processed with dithioerythritol (DTE) or PBS; recovery of eotaxin was assessed by means of ELISA before and after spiking with recombinant eotaxin. Furthermore, the effects of removing DTE by means of ultrafiltration or the addition of protease inhibitors and high-speed centrifugation on endogenous levels and spiking recovery of eotaxin were assessed.

RESULTS

Endogenous eotaxin was undetectable in DTE-processed samples, with a mean of only 30% (SD, 13%) spike recovery. DTE had no effect on the immunoassay capture antibody but dramatically reduced the detection of recombinant eotaxin. Removal of DTE from sputum before immunoassay did not improve detection, although it restored the recovery of a subsequent eotaxin spike. In contrast, PBS-processed sputum resulted in an eotaxin spike recovery of 101% (SD, 20%). Addition of protease inhibitors or high-speed centrifugation had no effect on eotaxin detection. By using this optimized protocol, eotaxin levels in PBS-processed sputum samples were found to be significantly increased in asthmatic sputum (P<.05).

CONCLUSION

Measurement of eotaxin by means of immunoassay is adversely affected by DTE, possibly through irreversible denaturation of epitopes, which makes eotaxin undetectable by using the immunoassay antibody. Sputum samples should be processed into PBS for assessment of eotaxin, which is present at increased levels in asthmatic sputum.

Contribution of eotaxin-1 to eosinophil chemotactic activity of moderate and severe asthmatic sputum

The CC chemokine eotaxin-1 (CCL11) is chemotactic for eosinophils, basophils, and type 2 helper T cells and may play a role in allergic inflammation. We investigated its contribution as an eosinophil chemoattractant in asthmatic airway secretions (sampled as induced sputum), which possess chemotactic activity for eosinophils and T cells. Sputum samples collected from healthy subjects and subjects with mild, stable-moderate, unstable-moderate, and severe asthma were processed with phosphate-buffered saline and assayed for eotaxin by ELISA and for eosinophil chemotactic activity by fluorescence-based chemotaxis assay. The contribution of eotaxin to chemotactic activity was studied by using a high-affinity neutralizing human anti-eotaxin antibody, CAT-213. Sputum eotaxin concentration was significantly raised in moderate and severe asthma (p < 0.05 versus healthy control subjects) but not in mild asthma. Chemotactic activity was significantly increased in all asthmatic groups relative to healthy subjects (p < 0.05) and was significantly inhibited by CAT-213 (100 nM) in subjects with moderate and severe asthma, with median inhibition of 52% (p < 0.05), 78% (p < 0.0001), and 86% (p < 0.0001), respectively, in samples representing stable-moderate, unstable-moderate, and severe asthma. Eotaxin contributed to the eosinophil chemotactic activity of sputum from subjects with more severe forms of asthma but not mild asthma, suggesting that its contribution is more important in more severe disease. This activity is inhibited significantly by CAT-213.

Surface-enhanced resonance Raman scattering of black inkjet dyes in solution and in situ printed onto paper

Understanding the changes that occur when dyes are absorbed onto paper is crucial for the design of new inkjet dyes. This problem is particularly difficult for black dyes that have complex chromophores, and as a result, spectroscopic information on electronic and structural changes can be of importance. Surface-enhanced resonance Raman scattering (SERRS) and electronic structure calculations were used to probe in situ changes in the chromophore in black di-azo dyes printed onto paper. The data indicate that the low-energy chromophore is due mainly to the hydrazone group and the high-energy chromophore to both the azo and hydrazone groups. A comparison of SERRS from the dyes adsorbed onto silver particles in suspension and from the dyes on paper demonstrated a broadening of the chromophore into the red for both dyes and evidence of a structural change in one dye.

Differential roles of IL-16 and CD28/B7 costimulation in the generation of T-lymphocyte chemotactic activity in the bronchial mucosa of mild and moderate asthmatic individuals

BACKGROUND

IL-16 is an important T-cell chemotactic cytokine in asthmatic airways; its release from allergen-stimulated bronchial mucosa in mild asthma has been shown to be dependent on CD28/B7 costimulation.

OBJECTIVE

We have extended our previous studies to investigate the role of IL-16 and CD28/B7 costimulation in T-lymphocyte chemotactic activity (TLCA) released from the bronchial mucosa in more severe asthma.

METHODS

TLCA was determined in the supernatants of induced sputum and allergen-stimulated bronchial mucosal explants from healthy volunteers and volunteers with mild and moderately severe asthma by means of a Boyden chamber technique. The contribution of IL-16 to the activity was evaluated through use of a neutralizing monoclonal antibody; the contribution of CD28/B7 costimulation to allergen-induced release of TLCA was determined through use of CTLA4-Ig fusion protein and neutralizing monoclonal antibodies to CD80 (B7.1) and CD86 (B7.2).

RESULTS

Induced sputum and unstimulated explants from asthmatic subjects generated significant spontaneous TLCA (P <.05). Both mild and moderate asthmatic explants showed significantly elevated Dermatophagoides pteronyssinus -induced release of TLCA, but only in mild asthma could sputum and allergen-stimulated explant TLCA be inhibited by anti-IL-16 (median inhibition, 39% and 59%; P <.05). In addition, allergen released significant quantities of IL-16 from mild asthmatic explants (P <.05) but not from moderate asthmatic explants. Antibodies to the CD28 counter-ligands CD80 and CD86 inhibited allergen-induced release of TLCA in mild asthmatic explants by 94% (P <.05) and 62%, but TLCA release from moderate asthmatic explants was unaffected by CTLA4-Ig.

CONCLUSION

These results show that TLCA release in moderate asthmatic airways, in contrast to mild asthmatic airways, is not dependent on CD28/B7 costimulation and does not involve IL-16.

Studying human airway pharmacology in microsections: application of videomicrometry

The influence of endogenously-released mediators and activated eosinophils on the airway lumen and the effect of passive sensitization on anti-immunoglobulin (Ig)-E-induced contractile responses was investigated by videomicrometry. Human bronchial sections of 2-3 mm internal diameter, placed in 250 microL Hank's balanced salt solution on microtitre plates, were monitored and recorded by digitized image analysis. Airway preparations exhibited a spontaneous narrowing (mean+/-SEM -33+/-5% of the luminal area). Removal of the bronchial epithelium almost completely prevented the development of spontaneuous narrowing (-6+/-3%; p<0.001). The addition of platelet-activating factor stimulated human eosinophils to the bronchial sections led to significant narrowing of the airway lumen (-39+/-9%; p<0.05). Passive sensitization induced hyperresponsiveness to polyclonal anti-IgE (-35+/-8%; p<0.01). It is concluded that videomicrometry is suitable for studying interactions between human airways and inflammatory cells, as well as the effect of passive sensitization on smooth muscle reactivity in vitro, without the imposition of preload. Under these conditions, human airways exhibited a spontaneous decrease of the airway lumen over time suggesting a role for epithelium-derived mediators because the development of spontaneous tone was epithelium dependent.

Ciclesonide ( Byk Gulden)

Ciclesonide, a non-halogenated inhaled corticosteroid with anti-inflammatory activity, is under development by Byk Gulden, Aventis and Teijin as a potential treatment for asthma [213439]. It was also being developed by Byk Gulden for chronic obstructive pulmonary disease (COPD), but no development had been reported for this indication since 1999; however, Teijin was carrying out clinical trials in this indication at the end of 2000. During 2000, Byk Gulden was carrying out phase III trials in the US and Europe and in March 2001, results were expected in the third quarter of 2001 [312399], [383726], [423659]. Two inhalant formulations (multidose powder and propellant filled) and a nasal formulation of ciclesonide are being developed by Byk Gulden for the treatment of asthma and seasonal allergic rhinitis, respectively [337147]. The compound is formulated for once-daily dosing and demonstrated good efficacy without corticosteroid-associated systemic side effects [409257]. In January 2001, Byk Gulden expected launch of a CFC-free multidose inhaler formulation in 2003 [395596]; in March 1999, launch of a nasal formulation was expected in 2004 and a multidose powder inhaler in 2005 [337147]. By September 2001, the compound was in phase III trials in the US for asthma, with a potential US launch anticipated by Aventis in 2004 [423465]. In November 2001, Aventis expected to submit an NDA to the FDA in 2003 [428057]. Teijin, which has a development and licensing agreement with Byk Gulden for the treatment of asthma and COPD in Japan, commenced phase I trials of ciclesonide in Japan in spring 1999, had completed these during 2000, and began phase II trials by September of that year [383726]. An NDA is expected to befiled in Japan in 2003. In October 2000 and April 2001, Merrill Lynch predicted peak sales of Euro400 million in 2007, with sales of Euro5 million in 2002, rising to Euro150 million in 2004 [395562], [420574]. Deutsche Bank predicted in August 2001, that sales of the product would reach Euro70 million in 2004, rising to Euro150 million in 2005 [420814].

The role of CD28-B7 costimulation in allergen-induced cytokine release by bronchial mucosa from patients with moderately severe asthma

BACKGROUND

T cells play an important role in airway inflammation in asthma through the release of T(H)2 cytokines. Optimal T-cell activation by antigen-presenting cells requires co-stimulatory signaling, such as the interaction of CD80, CD86, or both with CD28. In patients with mild allergic asthma, the fusion protein cytotoxic T-lymphocyte antigen 4Ig (CTLA-4Ig), which inhibits CD28-mediated signaling, blocks the release of IL-5 and IL-13 from bronchial explant cultures exposed to the allergen Dermatophagoides pteronyssinus.

OBJECTIVES

To assess costimulation in more severe forms of atopic asthma, we have compared the ability of CTLA-4Ig to block allergen-induced cytokine responses of bronchial explants and PBMCs from patients with moderately severe asthma.

METHODS

Bronchial explants and PBMCs were cultured in vitro, and cytokine expression was measured by means of quantitative RT-PCR and ELISA.

RESULTS

Constitutive mRNA transcripts for IL-5, IL-13, and GM-CSF were detected in the tissue explants, but only IL-5 mRNA increased significantly with allergen stimulation. Consistent with increased transcription, allergen-stimulated IL-5 protein release into explant supernatants, but this was not blocked by CTLA-4Ig. Allergen did not induce GM-CSF release, and IL-13 protein could not be detected in the explant supernatants under any condition. In contrast, allergen enhanced production of IL-5 and IL-13 by PBMC cultures from the same subjects, and this was inhibited effectively by CTLA-4Ig.

CONCLUSIONS

These data suggest that IL-5 production in the airways of subjects with moderately severe asthma is largely independent of CD28-mediated costimulation. The different requirements for CD28-mediated costimulation in PBMC cultures and bronchial tissue cultures emphasizes the importance of the tissue microenvironment in pulmonary inflammatory responses in severe asthma.

The contribution of interleukin (IL)-4 and IL-13 to the epithelial-mesenchymal trophic unit in asthma

Interleukin (IL)-4 and IL-13 are key proinflammatory cytokines in asthma. Studies in transgenic mice show that both cytokines cause inflammation, but only IL-13 causes subepithelial fibrosis, a characteristic feature of asthma. We compared the in vitro profibrogenic effects of IL-4 and IL-13 using bronchial fibroblasts from asthmatic subjects. In the presence of transforming growth factor (TGF)-beta the cells transformed into contractile myofibroblasts and expressed alpha-smooth muscle actin and procollagen I. IL-4 and IL-13 also stimulated proliferation, but were relatively ineffective in promoting myofibroblast transformation. TGF-beta was more potent than the cytokines in stimulating release of endothelin-1 and vascular endothelial growth factor, whereas IL-4 and IL-13 were more potent stimuli for eotaxin release. Although neither IL-4 nor IL-13 induced profibrotic responses, both cytokines caused a corticosteroid-insensitive stimulation of TGF-beta2 release from primary bronchial epithelial cells. These data indicate that epithelial activation by IL-13 or IL-4 plays a critical role in initiating remodeling through release of TGF-beta2. TGF-beta2 then activates the underlying myofibroblasts to secrete matrix proteins and smooth muscle and vascular mitogens to propagate remodeling changes into the submucosa. In contrast, direct activation of submucosal fibroblasts by IL-4 and IL-13 has a proinflammatory effect via eotaxin release and recruitment of eosinophils into the airways.

The effect of selective and non-selective phosphodiesterase inhibitors on allergen- and leukotriene C(4)-induced contractions in passively sensitized human airways

Non-selective inhibitors of cyclic nucleotide phosphodiesterase (PDE) block allergen-induced contraction of passively sensitized human airways in vitro by a dual mechanism involving a direct relaxant effect on smooth muscle and inhibition of histamine and cysteinyl leukotriene (LT) release from airways. We investigated the effects of non-selective PDE inhibitors and selective inhibitors of PDE3 and PDE4 in order to determine the involvement of PDE isoenzymes in the suppression of allergic bronchoconstriction. Macroscopically normal airways from 76 patients were sensitized with IgE-rich sera (>250 u ml(-1)) containing specific antibodies against allergen (Dermatophagoides farinae). Contractile responses of bronchial rings were assessed using standard organ bath techniques. Passive sensitization caused increased contractile responses to allergen, histamine and LTC(4). Non-selective PDE inhibitors (theophylline, 3-isobutyl-1-methylxanthine [IBMX]), a PDE3-selective inhibitor (motapizone), PDE4-selective inhibitors (RP73401, rolipram, AWD 12-281) and a mixed PDE3/4 inhibitor (zardaverine) all significantly relaxed inherent bronchial tone at resting tension and to a similar degree. Theophylline, IBMX, zardaverine and the combination of motapizone and RP73401 inhibited the contractile responses to allergen and LTC(4). Pre-treatment with motapizone, RP73401, rolipram or the methylxanthine adenosine receptor antagonist, 8-phenyltheophylline, did not significantly decrease responses to either allergen or LTC(4). We conclude that combined inhibition of PDE3 and PDE4, but not selective inhibition of either isoenzyme or antagonism of adenosine receptors, is effective in suppressing allergen-induced contractions of passively sensitized human airways. The relationship between allergen- and LTC(4)-induced responses suggests that PDE inhibitors with PDE3 and PDE4 selectivity are likely to act in part through inhibition of mediator release and not simply through direct relaxant actions on airway smooth muscle.

PNU-142731A Pharmacia

Pharmacia is developing PNU-142731A, a potential lead compound as a treatment for asthma [294718]. It is in phase I clinical trials. PNU-142731A is a potent inhibitor of eosinophilic lung inflammation in rodents, and shows a good bioavailability profile in animals; the mechanism of action is being investigated. Unlike the original compound PNU-104067F, PNU-142731A does not give rise to gall bladder toxicity [295987], [298023].

Involvement of protein tyrosine kinases in activation of human eosinophils by platelet-activating factor

Activation of human eosinophils by platelet-activating factor (PAF) involves multiple signal transduction pathways. Among these, protein kinase C has been demonstrated both to mediate respiratory burst and to suppress an alternative pathway of activation of respiratory burst and arachidonic acid metabolism in eosinophils. We utilized inhibitors of protein tyrosine kinases (PTK) to elucidate the role of PTK in PAF-induced activation of eosinophils. Eosinophils were isolated from peripheral blood of atopic donors and stimulated with PAF in the absence or presence of broad-spectrum PTK inhibitors-genistein or lavendustin A; an inhibitor of mitogen-activated protein (MAP) kinase activation-tyrphostin AG126; or an inhibitor of Janus kinase 2 (Jak2)-tyrphostin B42 (AG490). PAF induced superoxide anion (O2-*) generation, leukotriene C4 (LTC4) release, intracellular calcium ion mobilization and tyrosine phosphorylation of multiple eosinophil proteins in a concentration-dependent manner. All of these responses were concentration-dependently inhibited by genistein; lavendustin A also exhibited potent inhibition of PAF-induced LTC4 release. AG126 had no effect on either O2-* generation or LTC4 release, while AG490 inhibited both responses, albeit less effectively than genistein. We conclude that PAF activates PTK in human eosinophils and that this signalling pathway is involved in eliciting respiratory burst and leukotriene production. The specific PTK(s) involved are unknown but may include Jak2.

Up-regulation of human eosinophil leukotriene C4 generation through contact with bronchial epithelial cells

OBJECTIVE AND DESIGN

We studied the effect of contact with bronchial epithelial cells on the functional activity of human eosinophils, measured as the production of a bronchoconstrictor lipid mediator, leukotriene C4 (LTC4) to determine the role of cell-cell interaction in activation of airway eosinophils.

MATERIALS AND METHODS

Eosinophils were isolated from peripheral blood of atopic donors. Epithelial cells were obtained from the bronchi of surgically resected lung lobes and cultured to confluence on collagen-coated plates. Eosinophils were stimulated with platelet activating factor (PAF) or serum opsonized zymosan (SOZ) after incubation with or without epithelial cells. Leukotriene C4 (LTC4) was assayed in supernatants by enzyme immunoassay.

RESULTS

Bronchial epithelial cells did not produce LTC4 in response to PAF or SOZ. Eosinophils pre-incubated in collagen-coated plates for 1 h produced LTC4 in response to both PAF (130 +/- 53 fmol/10(6) eosinophils at 10 micromol/l PAF, 5 min) and SOZ (1,900 +/- 550 fmol/10(6) eosinophils at 2 mg/ml SOZ, 15 min). Eosinophils co-incubated with bronchial epithelial cells for 1 h produced significantly higher quantities of LTC4 in response to both PAF (310 +/- 94 fmol/10(6) eosinophils; P<0.01) and SOZ (5,500 +/- 1,500 fmol/10(6) eosinophils; P<0.001). Ligation of the common beta2 integrin subunit (CD18) with a monoclonal antibody inhibited PAF-stimulated and augmented SOZ-stimulated LTC4 generation by eosinophils alone but had marginal effects on the epithelium-dependent up-regulation.

CONCLUSIONS

Contact with bronchial epithelial cells up-regulates the responsiveness of human eosinophils, a finding that has significant implications in the pathology of asthma.

Phosphodiesterase and cyclic adenosine monophosphate-dependent inhibition of T-lymphocyte chemotaxis

There is abundant evidence for T-lymphocyte recruitment into the airways in allergic inflammatory responses. This study has tested the hypothesis that T-cell chemotaxis induced by platelet-activating factor (PAF) and human recombinant interleukin-8 (hrIL-8) can be attenuated by inhibition of phosphodiesterase activity and raised intracellular 3',5'-cyclic adenosine monophosphate (cAMP) levels. This study used theophylline, a nonselective phosphodiesterase (PDE) inhibitor, and rolipram, a selective PDE4 inhibitor, to study the effect of PDE inhibition on T-cell chemotaxis. The beta2-adrenoceptor agonist, salbutamol, the adenylyl cyclase activator, forskolin, and the cAMP analogue, dibutyryl cAMP (db-cAMP), were used to demonstrate a role for raised cAMP levels. T-cells were obtained from 10 atopic asthmatics, and the phenotype of migrating cells was examined by flow cytometry. Theophylline caused an inhibition of both PAF-and hrIL-8-induced chemotaxis (mean+/-SEM maximum inhibition at 1 mM: 73+/-4% and 48+/-8% for hrIL-8 and PAF, respectively) that was not specific for the CD4+, CD8+, CD45RO+ or CD45RA+ T-cell subsets. T-cell chemotaxis was more sensitive to treatment with rolipram whose effect was already significant from 0.1 microM on hrIL-8-induced chemotaxis. Both a low concentration of salbutamol (0.1 mM) and forskolin (10 microM) potentiated the inhibitory effect of a low concentration of theophylline (25 microM) on responses to PAF but not to hrIL-8. Finally, T-cell chemotaxis was also inhibited by db-cAMP. It is concluded that attenuation of T-cell chemotaxis to two chemoattractants of relevance to asthma pathogenesis can be achieved via phosphodiesterase inhibition and increased intracellular 3', 5'-cyclic monophosphate using drugs active on cyclic nucleotide phosphodiesterase. This action may explain the anti-inflammatory effects of theophylline and related drugs in asthma.

Selective phosphodiesterase inhibitors for the treatment of bronchial asthma and chronic obstructive pulmonary disease

Theophylline is commonly used in the treatment of obstructive airway diseases. The identification and functional characterization of different phosphodiesterase (PDE) isoenzymes has led to the development of various isoenzyme-selective inhibitors as potential anti-asthma drugs. Considering the distribution of isoenzymes in target tissues, with high activity of PDE3 and PDE4 in airway smooth muscle and inflammatory cells, selective inhibitors of these isoenzymes may add to the therapy of chronic airflow obstruction. However, initial data from clinical trials with selective PDE3 and PDE4 inhibitors have been somewhat disappointing and have tempered the expectations considerably since these drugs had limited efficacy and their use was clinically limited through side effects. The improved understanding of the molecular biology of PDEs enabled the synthesis of novel drugs with an improved risk/benefit ratio. These 'second generation' selective drugs have produced more promising clinical results not only for the treatment of bronchial asthma but also for the treatment of chronic obstructive pulmonary disease.

Theophylline and airway inflammation

The view of theophylline as a second-line bronchodilator in asthma therapy has begun to be reconsidered in recent years as the details of its additional actions on airway inflammation have emerged. Increasing understanding of the mechanisms of action of theophylline has led to an appreciation of the ways in which this, and other related drugs, may influence the development and maintenance of the airway inflammation that underlies asthma through alteration of inflammatory cell function. In addition, recent demonstrations that theophylline can suppress late-phase asthmatic reactions at serum concentrations below those traditionally regarded as therapeutically useful have provided evidence that theophylline's beneficial actions in asthma extend beyond mild bronchodilation. The apparent suppression of airway inflammation by theophylline in asthmatic patients reinforces data from ill vitro experiments, showing inhibitory actions of theophylline on the pro-inflammatory functions of many immune cells. Here, we review some recent advances in the understanding of theophylline's actions that suggest its role as an anti-inflammatory drug in asthmatic airways.

Inhibition of human airway sensitization by a novel monoclonal anti-IgE antibody, 17-9

We investigated the effect of a novel mouse IgG2b nonanaphylactogenic anti-human IgE antibody, 17-9, on allergen and histamine responses in passively sensitized human airways in vitro to determine the specific contribution of IgE to the sensitization process. Bronchial rings were sensitized with serum containing high levels of allergen-specific IgE (Dermatophagoides farinae), or with a hapten-specific chimeric humanized IgE (JW8). There was a concentration-dependent contraction of serum-sensitized bronchial rings to D. farinae (517 +/- 188 mg tension at 10 U/ml, n = 8) that was not observed in nonsensitized controls. This response was practically abolished when tissues were sensitized in the presence of 100 microg/ml anti-IgE antibody 17-9 (54 +/- 20 mg). In tissues sensitized with the anti-NIP IgE, JW8, there was a concentration-dependent contraction to the specific antigen NIP-BSA (560 +/- 154 mg at 0.3 microg/ml, n = 5) that was not observed in nonsensitized control subjects and that was substantially inhibited when 17-9 was present in the sensitization buffer (124 +/- 109 mg). The inhibition with 17-9 was specific, as pretreatment with a non-IgE-specific IgG2b antibody did not affect allergen responses. Potency and maximal contractions to histamine in serum-sensitized tissues were significantly elevated compared with nonsensitized controls; this was not affected by the presence of 17-9 during sensitization (pEC50 = 5.1 +/- 0.2 versus 5.0 +/- 0.3 in tissues sensitized in the absence of 17-9). In tissues sensitized with JW8 there was no significant increase in responsiveness to histamine. We conclude that allergen responses in sensitized human airways are dependent on IgE levels in the sensitizing serum while nonspecific (hyper)responsiveness depends on serum factors other than IgE. Nonanaphylactogenic anti-human IgE antibodies effectively inhibit allergen responses of human airways in vitro but may not affect other factors inducing hyperresponsiveness.

Effects of a 5-lipoxygenase inhibitor, ABT-761, on exercise-induced bronchoconstriction and urinary LTE4 in asthmatic patients

The novel 5-lipoxygenase (5-LO) inhibitor, ABT-761, was investigated for its effect on exercise-induced bronchoconstriction in asthmatic subjects. The relationship between 5-LO inhibition and effects on the response of the airways to exercise was examined. In a double-blind, randomized, crossover clinical trial, 10 patients with mild to moderate persistent asthma (who exhibited a fall in forced expiratory volume in one second (FEV1) > or = 20% following standardized exercise challenge) received 200 mg ABT-761 or matched placebo, orally, 5 h prior to exercise on two study days, 7-10 days apart. Lung function, urinary leukotriene E4 (LTE4) and ex vivo calcium ionophore-stimulated LTB4 release in whole blood were measured prior to dosing, prior to exercise and at various time points up to 4 h post-exercise. The mean (SD) maximal percentage fall in FEV1 after exercise was 27.1 (12)% on placebo and 19.9 (10)% on ABT-761 days, respectively (p<0.05). Post-exercise fall in FEV1 was significantly attenuated at 5, 10, 15 and 30 min after exercise and the mean area under curve, representing the overall effect of exercise from 0-45 min post-challenge, was also significantly attenuated by ABT-761 (p<0.001). Ex vivo LTB4 release was inhibited by more than 80% throughout the 4 h post-exercise period, indicating that 5-LO was extensively inhibited at all time points. Urinary LTE4 in the post-exercise period was significantly lower after ABT-761 day than after placebo (40.1 (17.6) versus 89.8 (58.2) pg x mg creatinine(-1); p<0.05). Inhibition of LTB4 release in ABT-761-treated patients correlated positively with the attenuation of post-exercise FEV1 decline (r=0.711; p<0.05). We conclude that ABT-761 is effective in suppressing exercise-induced bronchoconstriction and that this protection is related quantitatively to the degree of 5-lipoxygenase inhibition.

Effects of a 5-lipoxygenase inhibitor, ABT-761, on exercise-induced bronchoconstriction and urinary LTE4 in asthmatic patients

The novel 5-lipoxygenase (5-LO) inhibitor, ABT-761, was investigated for its effect on exercise-induced bronchoconstriction in asthmatic subjects. The relationship between 5-LO inhibition and effects on the response of the airways to exercise was examined. In a double-blind, randomized, crossover clinical trial, 10 patients with mild to moderate persistent asthma (who exhibited a fall in forced expiratory volume in one second (FEV1) > or = 20% following standardized exercise challenge) received 200 mg ABT-761 or matched placebo, orally, 5 h prior to exercise on two study days, 7-10 days apart. Lung function, urinary leukotriene E4 (LTE4) and ex vivo calcium ionophore-stimulated LTB4 release in whole blood were measured prior to dosing, prior to exercise and at various time points up to 4 h post-exercise. The mean (SD) maximal percentage fall in FEV1 after exercise was 27.1 (12)% on placebo and 19.9 (10)% on ABT-761 days, respectively (p<0.05). Post-exercise fall in FEV1 was significantly attenuated at 5, 10, 15 and 30 min after exercise and the mean area under curve, representing the overall effect of exercise from 0-45 min post-challenge, was also significantly attenuated by ABT-761 (p<0.001). Ex vivo LTB4 release was inhibited by more than 80% throughout the 4 h post-exercise period, indicating that 5-LO was extensively inhibited at all time points. Urinary LTE4 in the post-exercise period was significantly lower after ABT-761 day than after placebo (40.1 (17.6) versus 89.8 (58.2) pg x mg creatinine(-1); p<0.05). Inhibition of LTB4 release in ABT-761-treated patients correlated positively with the attenuation of post-exercise FEV1 decline (r=0.711; p<0.05). We conclude that ABT-761 is effective in suppressing exercise-induced bronchoconstriction and that this protection is related quantitatively to the degree of 5-lipoxygenase inhibition.

Cyclic nucleotide phosphodiesterase in human bronchial epithelial cells: characterization of isoenzymes and functional effects of PDE inhibitors

Cyclic AMP (adenosine 3':5'-cyclic monophosphate, cAMP) is an intracellular second messenger that mediates the actions of endogenous hormones and neurotransmitters and also of drugs such as beta-adrenoceptor agonists. The presence of functional beta-adrenoceptors on human airway epithelial cells has been demonstrated but the expression of the cAMP-metabolizing enzyme, cyclic nucleotide phosphodiesterase (PDE) in these cells has not been studied. We investigated the profile of activity of the different PDE isoenzymes in lysates of a pulmonary epithelial cell line, A549, and of human bronchial epithelial (HBE) cells grown in primary culture. The effects of non-selective and isoenzyme-selective PDE inhibitors on beta-agonist-induced elevations in intracellular cAMP concentrations and the production of interleukin (IL) 8 and prostaglandin (PG) E2 was also investigated. A549 cells expressed a high level of PDE4, lower levels of PDE1 and PDE3, and minor PDE5 activity. Primary HBE cultures expressed PDE4 and PDE1 activity at approximately equal levels with small additional PDE3 and PDE5 activities. The total PDE activity of the HBE cells was approximately nine-fold lower than that of A549 cells. The beta-adrenoceptor agonist salbutamol, caused a slow, concentration-dependent increase in intracellular cAMP levels in HBE cells which was not affected by a non-selective PDE inhibitor, IBMX (100 microM), or by a selective PDE4 inhibitor, rolipram (100 microM). Zardaverine, a dual-selective PDE3/PDE4 inhibitor, had no effect on cAMP levels at 10 microM but did cause a significant enhancement of salbutamol-induced elevations at 100 microM (150+/-36 pmol/10(5) cells at 10 microM salbutamol vs. 64+/-25 pmol/10(5) cells in the absence of zardaverine; n=3,P<0.01). Neither basal nor tumour necrosis factor alpha (10 ng/ml)-induced IL8 secretion was affected by salbutamol (10 microM) in the absence or presence of IBMX (100 microM). Salbutamol (10 microM), alone or in the presence of IBMX (100 microM) or rolipram (100 microM), also failed to affect basal or bradykinin (1 microM)-induced PGE2 release. Zardaverine (100 microM) caused a significant increase in basal PGE2 release but this was not enhanced in the presence of salbutamol (10 microM) and was not related to changes in cAMP levels. We conclude that HBE cells express a low total PDE activity, made up predominantly of PDE1 and PDE4 isoenzymes, and that intracellular cAMP levels in HBE cells are not related to the production of IL8 or PGE2.

Effects of a selective PDE4 inhibitor, D-22888, on human airways and eosinophils in vitro and late phase allergic pulmonary eosinophilia in guinea pigs

The actions of a novel selective inhibitor of type 4 cyclic nucleotide phosphodiesterase (PDE4), D-22888, on human airway smooth muscle tone and human eosinophil respiratory burst in vitro and bronchoalveolar eosinophilia in allergen-challenged sensitized guinea pigs in vivo were assessed. D-22888 was a selective inhibitor of PDE4, exhibiting an IC50 against human neutrophil PDE4 of 0.15 microM, compared to IC 50 values of 4.4 microM and 1.1 microM for human platelet PDE3 and PDE5, respectively. D-22888 relaxed inherent tone in human bronchial rings in a concentration-dependent manner with an IC50 of 5.0 microM (geometric mean, 95% ci 3.0-8.4 microM) and also caused a concentration-dependent inhibition of opsonized zymosan-induced superoxide anion generation by human eosinophils with an IC50 of 3.1 microM (1.0-9.2 microM). Treatment of actively sensitized guinea pigs with single oral doses of D-22888 2 h before or 4 h after challenge reduced bronchoalveolar lavage (BAL) eosinophil numbers, 24 h after aerosol allergen challenge, by 48% and 73% at 10 mg/kg and 30 mg/kg, respectively, 2 h pre-challenge and 68% at 30 mg/kg 4 h post-challenge. Chronic twice-daily oral dosing with D-22888 for three days caused inhibition of 24 h post-challenge BAL eosinophilia, amounting to 88% at 30 mg/kg. These in vivo actions were comparable with those achieved with other selective PDE4 inhibitors and with the corticosteroid, dexamethasone. We conclude that D-22888 exerts actions on airway smooth muscle and eosinophil recruitment and activation that suggest that D-22888 may be a promising new drug for use in the treatment of allergic obstructive airways>> diseases such as bronchial asthma.

Protein kinase C inhibition enhances platelet-activating factor-induced eicosanoid production in human eosinophils

Previous investigations have suggested that protein kinase C (PKC) may regulate guinea pig eosinophil responses through a suppressive "negative feedback" mechanism. Using the selective PKC inhibitors bisindolylmaleimide I (Bis I, GF 109203X) and calphostin C, we examined the role of PKC in platelet-activating factor (PAF)-induced respiratory burst and generation of arachidonic acid metabolites in human peripheral blood eosinophils. Bis I inhibited PAF-induced generation of superoxide anion with substantially lower potency (geometric mean IC50 = 1.41 microM, 95% CI 0.94-2.11 microM) than it exhibited against responses to the phorbol esters 4-beta-phorbol 12-myristate 13-acetate (PMA; IC50 = 0.25 microM, 0.09-0.72 microM; P < 0.01) and 4-beta-phorbol 12,13-dibutyrate (IC50 = 0.48 microM, 0.20-1.14 microM; P < 0.05). The production of thromboxane (measured as TxB2) induced by 1 microM PAF was increased significantly by Bis I at concentrations of 1 microM (162 +/- 7.5% of control PAF response; P < 0.01) and 10 microM (194 +/- 17%; P < 0.001); TxB2 release induced by PMA was unaffected by concentrations of Bis I up to 1 microM and inhibited by 10 microM Bis I (48 +/- 11%; P < 0.05). Bis I (1 microM) significantly increased both thromboxane and leukotriene C4 (LTC4) production induced by 2 microM (P < 0.01 and P < 0.05, respectively) or 20 microM PAF (both P < 0.001). The actions of Bis I on PAF-stimulated thromboxane and leukotriene production were mimicked by a second PKC inhibitor, calphostin C, whereas the non-PKC-inhibitory analog, bisindolylmaleimide V, caused no enhancement of TxB2 or LTC4 production. The increase in intracellular free calcium induced by 1 microM PAF was heightened and prolonged in cells pre-treated with 1 microM Bis I or 1 microM calphostin C (peak increase, P < 0.05 for both drugs; level 60 s after addition of PAF, P < 0.001 and P < 0.05 for Bis I and calphostin C, respectively; time to return to 50% of peak, P < 0.05 for Bis I). We conclude that PKC inhibition causes augmentation of thromboxane and LTC4 production in PAF-stimulated human eosinophils despite suppressing respiratory burst activity, indicating that different signaling pathways predominate in these two responses and that PKC mediates a suppression of an early stage in an alternative pathway of activation.

Augmentation of human neutrophil and alveolar macrophage LTB4 production by N-acetylcysteine: role of hydrogen peroxide

1. The actions of N-acetylcysteine (NAC) on hydrogen peroxide (H2O2) and leukotriene B4 (LTB4) production by human resting and stimulated peripheral blood neutrophils and alveolar macrophages were investigated. 2. At a concentration of 100 microM, NAC significantly (P < 0.01) suppressed the accumulation of H2O2 in the incubation medium of resting and opsonized zymosan (OZ; 0.5 mg ml[-1])- or N-formylmethionyl-leucyl-phenylalanine (fMLP; 1 microM)-stimulated neutrophils and of resting and OZ-stimulated macrophages. At concentrations of 10 microM and above, NAC augmented significantly the level of LTB4 in the supernatants of OZ- and fMLP-stimulated neutrophils (P < 0.01 and P < 0.05, respectively) and OZ-stimulated macrophages (P < 0.05 at 10 microM, P < 0.01 at 100 microM NAC). 3. NAC (100 microM) caused a significant (P < 0.01) reduction in the quantity of measurable H2O2 when incubated with exogenous H2O2 concentrations equivalent to those released from OZ-stimulated neutrophils and macrophages. At no concentration did NAC affect quantitites of measurable LTB4 when incubated with exogenous LTB4. 4. Superoxide dismutase (SOD), which catalyzes the conversion of superoxide anion to H2O2 had no significant effect on LTB4 production by human neutrophils. In contrast, catalase, which catalyzes the conversion of H2O2 to H2O and O2, caused a pronounced, statistically significant (P < 0.01) increase in the levels of LTB4 measured in the supernatants of OZ- and fMLP-stimulated neutrophils. 5. H2O2 (12.5 microM and 25 microM, concentrations equivalent to those measured in the supernatants of activated neutrophils and alveolar macrophages, respectively) caused a small (13%) decrease in the quantity of measurable LTB4 (P = 0.051 and P < 0.05 at 12.5 microM and 25 microM, respectively) that was inhibited by NAC (100 microM) but not by catalase (400 u ml[-1]). 6. In conclusion, the anti-oxidant drug, NAC, increases LTB4 production by human neutrophils and alveolar macrophages, probably through the elimination of cell-derived H2O2. LTB4 undergoes a H2O2-dependent oxidation that is inhibited by NAC but this is unlikely to account fully for the increased levels of LTB4, suggesting that NAC may increase LTB4 production by blocking the H2O2-dependent inhibition of a synthetic enzyme, such as 5-lipoxygenase.

A method for the production of CD4+ chronic myelogenous leukemia-specific allogeneic T lymphocytes

The graft-versus-leukemia effect is critical to the maintenance of remission in patients transplanted for the treatment of chronic myelogenous leukemia (CML). A pivotal issue in transplantation for CML is whether donor lymphocytes are specific for host tumor or myeloid cells or a subset of the lymphocytes that cause graft-versus-host disease. We have enrolled seven patients in an experimental trial to evaluate the specificity of HLA-matched donor lymphocytes in vitro. We have produced 11 CD4+ cytotoxic and proliferative T-cell clones from five of the donors that only lyse or proliferate to leukemic myeloid cells. These T lymphocytes do not react with interleukin (IL)-2-stimulated blasts, natural killer-sensitive targets, donor neutrophils, or bcr-abl+ EBV-lymphoblastoid cell lines. We show that the addition of the cytokines IL-7 and IL-12 during the production of T-cell clones enhances the recovery of myeloid-specific clones in vitro. Five of the myeloid-specific clones that we produced maintained specificity over 12 weeks in culture. Adoption of this method should allow for the expansion and in vivo testing of CML-specific CD4+ T-cell clones in adoptive immunotherapy.

Role of IgE in hyperresponsiveness induced by passive sensitization of human airways

Incubation of airways from nonatopic patients with serum from patients with high IgE levels confers responsiveness to "specific" (allergen) and hyperresponsiveness to "nonspecific" (histamine) stimuli. We have tested the hypothesis that the level of IgE determines the degree of specific and nonspecific responsiveness. Bronchial rings from nonatopic patients were sensitized overnight with serum containing high levels of allergen-specific IgE, or with an allergen-specific chimeric IgE (JW8) in physiologic buffer. In vitro responsiveness to allergen and histamine was evaluated and compared with non-sensitized tissues from the same patients. Responses to specific allergen were demonstrated in all tissues sensitized with atopic serum or chimeric IgE, but not in nonsensitized tissues. Allergen responses were specific, since tissues sensitized using serum containing high Dermatohagoides farinae-specific IgE only, did not respond to either horse or dog allergens. The potency and magnitude of the maximal contraction to histamine was significantly (p < 0.05) increased in tissues sensitized using atopic serum with high total IgE concentrations compared with nonsensitized preparations, but was unchanged in tissues sensitized using chimeric IgE or serum with low total IgE levels. Therefore, specific IgE determines allergen responsiveness in passively sensitized human airways, but histamine hyperresponsiveness is independent of specific IgE and appears to be related to some other factor associated with serum containing high concentrations of total IgE.

Phosphodiesterase inhibitors: Lily the Pink's medicinal compound for asthma?

The second messenger cyclic nucleotides, cyclic AMP and cyclic GMP, mediate relaxation of airways smooth muscle and suppression of multiple inflammatory cell functions. The intracellular concentrations of these cyclic nucleotides are regulated by a superfamily of phosphodiesterase (PDE) enzymes which break down cAMP and cGMP and, thereby, affect airway tone and inflammation. Theophylline and other drugs that act through inhibition of PDE are currently the subject of great research interest, since the uncovering of their anti-inflammatory actions suggests a possible additional mode of action in inflammatory diseases such as asthma. The characterisation of multiple families of PDE isoenzymes with distinct tissue distributions has encouraged hope that selective PDE inhibitors can be developed which act at specific targets without exhibiting the side effects of non-selective inhibitors like theophylline. The combination of bronchodilator and anti-inflammatory properties in a single drug by selective inhibition of specific PDE isoenzymes could produce agents most efficacious in every way for asthma therapy.

Hydrogen peroxide contracts human airways in vitro: role of epithelium

The effects of hydrogen peroxide (H2O2) on human airway smooth muscle tone were determined in vitro. Treatment with H2O2 led to transient concentration-related contractions in the organ bath, amounting to 118 +/- 14 mg (mean +/- SE; n = 12) at 1 mM H2O2, and to greater and more prolonged contractions under superfusion conditions, amounting to 451 +/- 71 mg (n = 17) at 1 mM H2O2. Epithelial removal augmented the response to H2O2 in both systems. Addition of catalase (500 U/ml) abolished the effects of H2O2. Pretreatment of superfused tissues with indomethacin (3 microM) shifted the concentration-effect curve to H2O2 rightward and almost abolished the response to 1 mM H2O2 in epithelium-intact preparations (n = 16; P < 0.05); the response in epithelium-denuded tissues was also significantly inhibited (n = 16; P < 0.05). Pretreatment of the tissues with the TP prostanoid-receptor antagonist GR-32191B (1 microM) also inhibited the contractile effect of H2O2 in epithelium-intact and -denuded tissues. In separate experiments, H2O2 resulted in concentration-related generation of prostaglandin (PG) D2 from isolated airway preparations. The amount of PGD2 released was not different in tissues with intact epithelium compared with those without (n = 9; NS). We conclude that H2O2 exerts on isolated human airways a contractile effect that is augmented by epithelium removal and is largely mediated by prostanoids. The source of PGD2 does not appear to be the epithelium, which we suggest serves mainly as a barrier against H2O2-mediated bronchoconstriction.