Interaction between prostaglandin D and chemoattractant receptor-homologous molecule expressed on Th2 cells mediates cytokine production by Th2 lymphocytes in response to activated mast cells

Severe asthma beyond bronchodilators: Emerging therapeutic approaches

Asthma is characterized by reversible airway inflammation, obstruction, and structural remodeling, which lead to the eosinophils and lymphocytes accumulation at inflammation sites and the release of inflammatory cells, like mast cells and dendritic cells, from lungs' epithelial and smooth muscle cells that trigger the activation and release of cytokines and chemokines, attracting more cells and contributing to asthma development. Available pharmacological interventions, like bronchodilators and anti-inflammatory agents, are considered generally safe and effective to treat asthma, but many affected individuals with severe asthma still struggle with symptom control. This review highlights recent innovative therapies, such as chemoattractant receptor-homologous molecule expressed on Th2 cell (CRTH2) antagonists, S-nitrosoglutathione reductase (GSNOR) and phosphodiesterase (PDE) inhibitors, and other novel biological agents, which offer potential new strategies for managing severe asthma and may alter the disease's course. Kew words. Inflammation; CRTH2; GSNOR; PDE; Interleukins; Biological agents.

Transcriptomic characterization of lung pericytes in systemic sclerosis-associated pulmonary fibrosis

Systemic sclerosis (SSc) is a chronic disease characterized by fibrosis and vascular abnormalities in the skin and internal organs, including the lung. SSc-associated pulmonary fibrosis (SSc-PF) is the leading cause of death in SSc patients. Pericytes are key regulators of vascular integrity and endothelial function. The role that pericytes play in SSc-PF remains unclear. We compared the transcriptome of pericytes from SSc-PF lungs (SScL) to pericytes from normal lungs (NORML). We identified 1,179 differentially expressed genes in SScL pericytes. Pathways enriched in SScL pericytes included prostaglandin, PI3K-AKT, calcium, and vascular remodeling signaling. Decreased cyclic AMP production and altered phosphorylation of AKT in response to prostaglandin E2 in SScL pericytes demonstrate the functional consequence of changes in the prostaglandin pathway that may contribute to fibrosis. The transcriptomic signature of SSc lung pericytes suggests that they promote vascular dysfunction and contribute to the loss of protection against lung inflammation and fibrosis.

Th2 cell clonal expansion at diagnosis in human type 1 diabetes

Soon after diagnosis with type 1 diabetes (T1D), many patients experience a period of partial remission. A longer partial remission is associated with a better response to treatment, but the mechanism is not known. The frequency of CD4+CD25+CD127hi (127-hi) cells, a cell subset with an anti-inflammatory Th2 bias, correlates positively with length of partial remission. The purpose of this study was to further characterize the nature of the Th2 bias in 127-hi cells. Single cell RNA sequencing paired with TCR sequencing of sorted 127-hi memory cells identifies clonally expanded Th2 clusters in 127-hi cells from T1D, but not from healthy donors. The Th2 clusters express GATA3, GATA3-AS1, PTGDR2, IL17RB, IL4R and IL9R. The existence of 127-hi Th2 cell clonal expansion in T1D suggests that disease factors may induce clonal expansion of 127-hi Th2 cells that prolong partial remission and delay disease progression.

Th2A cells: The pathogenic players in allergic diseases

Proallergic type 2 helper T (Th2A) cells are a subset of memory Th2 cells confined to atopic individuals, and they include all the allergen-specific Th2 cells. Recently, many studies have shown that Th2A cells characterized by CD3+ CD4+ HPGDS+ CRTH2+ CD161high ST2high CD49dhigh CD27low play a crucial role in allergic diseases, such as atopic dermatitis (AD), food allergy (FA), allergic rhinitis (AR), asthma, and eosinophilic esophagitis (EoE). In this review, we summarize the discovery, biomarkers, and biological properties of Th2A cells to gain new insights into the pathogenesis of allergic diseases.

The impact of CRTH2 antagonist OC 000459 on pulmonary function of asthma patients: a meta-analysis of randomized controlled trials

Introduction

The chemoattractant receptor expressed on T-helper (Th) type 2 cells (CRTH2) antagonist OC 000459 showed the potential in improving pulmonary function of asthma patients.

Aim

We conducted a systematic review and meta-analysis to explore the impact of CRTH2 antagonist OC 000459 on pulmonary function for asthma.

Material and methods

PubMed, Embase, Web of science, EBSCO, and Cochrane library databases were systematically searched. This meta-analysis included randomized controlled trials (RCTs) assessing the effect of CRTH2 antagonist OC 000459 on pulmonary function for asthma. Two investigators independently searched articles, extracted data, and assessed the quality of included studies.

Results

Four RCTs were included in the meta-analysis. Overall, compared with the control intervention for asthma patients, CRTH2 antagonist OC 000459 could significantly improve FEV₁ (SMD = 0.22; 95% CI: 0.02–0.42; p = 0.03), peak expiratory flow (SMD = 0.22; 95% CI: 0.01–0.42; p = 0.04) and reduce the respiratory tract infection (RR = 0.47; 95% CI: 0.26–0.85; p = 0.01), but revealed no remarkable effect on predicted FEV₁ (SMD = 0.14; 95% CI: –0.18 to 0.45; p = 0.39), or treatment-related adverse events (RR = 0.84; 95% CI: 0.52–1.36; p = 0.48).

Conclusions

CRTH2 antagonist OC 000459 might be effective and safe to improve pulmonary function in asthma patients.

Regulation of Eosinophilia in Asthma-New Therapeutic Approaches for Asthma Treatment

Asthma is a complex and chronic inflammatory disease of the airways, characterized by variable and recurring symptoms, reversible airflow obstruction, bronchospasm, and airway eosinophilia. As the pathophysiology of asthma is becoming clearer, the identification of new valuable drug targets is emerging. IL-5 is one of these such targets because it is the major cytokine supporting eosinophilia and is responsible for terminal differentiation of human eosinophils, regulating eosinophil proliferation, differentiation, maturation, migration, and prevention of cellular apoptosis. Blockade of the IL-5 pathway has been shown to be efficacious for the treatment of eosinophilic asthma. However, several other inflammatory pathways have been shown to support eosinophilia, including IL-13, the alarmin cytokines TSLP and IL-33, and the IL-3/5/GM-CSF axis. These and other alternate pathways leading to airway eosinophilia will be described, and the efficacy of therapeutics that have been developed to block these pathways will be evaluated.

Deficiency of CRTH2, a Prostaglandin D2 Receptor, Aggravates Bleomycin-induced Pulmonary Inflammation and Fibrosis

Chemoattractant receptor homologous with T-helper cell type 2 cells (CRTH2), a receptor for prostaglandin D₂, is preferentially expressed on T-helper cell type 2 lymphocytes, group 2 innate lymphoid cells, eosinophils, and basophils, and elicits the production of type 2 cytokines, including profibrotic IL-13. We hypothesized that lack of CRTH2 might protect against fibrotic lung disease, and we tested this hypothesis using a bleomycin-induced lung inflammation and fibrosis model in CRTH2-deficient (CRTH2^-/-) or wild-type BALB/c mice. Compared with wild-type mice, CRTH2^-/- mice treated with bleomycin exhibited significantly higher mortality, enhanced accumulation of inflammatory cells 14-21 days after bleomycin injection, reduced pulmonary compliance, and increased levels of collagen and total protein in the lungs. These phenotypes were associated with decreased levels of IFN-γ, IL-6, IL-10, and IL-17A in BAL fluid. Adoptive transfer of splenocytes from wild-type, but not CRTH2^-/-, mice 2 days before injection of bleomycin resolved the sustained inflammation as well as the increased collagen and protein accumulation in the lungs of CRTH2^-/- mice. We consider that the disease model is driven by γδT cells that express CRTH2; thus, the adoptive transfer of γδT cells could ameliorate bleomycin-induced alveolar inflammation and fibrosis.

Modulation of CRTh2 expression on allergen-specific T cells following peptide immunotherapy

Background

Allergen immunotherapy using synthetic peptide T‐cell epitopes (Cat‐PAD) from the major cat allergen Fel d 1 has been shown, in allergen exposure studies, to significantly reduce symptoms of allergic rhinoconjunctivitis in cat‐allergic subjects. However, the immunological mechanisms underlying clinical benefit remain only partially understood. Since previous studies of whole allergen immunotherapy demonstrated a reduction in the frequency of allergen‐specific (MHC II tetramer⁺) CD4⁺ T cells expressing the chemokine receptor CRTh2, we assessed the impact of Cat‐PAD on the frequency and functional phenotype of Fel d 1‐specific CD4⁺ T cells.

Methods

Using before and after treatment samples from subjects enrolled in a randomized, double‐blind, placebo‐controlled trial of Cat‐PAD, we employed Fel d 1 MHC II tetramers and flow cytometry to analyze the expression of chemokine receptors CCR3, CCR4, CCR5, CXCR3, and CRTh2, together with markers of memory phenotype (CD27 and CCR7) on Fel d 1‐specific CD4⁺ T cells.

Results

No statistically significant change in the frequency of Fel d 1‐specific CD4⁺ T cells, nor in their expression of chemokine receptors or memory phenotype, was observed. However, a significant reduction in cell surface expression of CRTh2 was observed between the placebo and active groups (P = 0.047).

Conclusions

Peptide immunotherapy with Cat‐PAD does not significantly alter the frequency or phenotype of Fel d 1‐CD4⁺ T cells, but may decrease their expression of CRTh2.

Cytokine-induced endogenous production of prostaglandin D2 is essential for human group 2 innate lymphoid cell activation

BACKGROUND

Group 2 innate lymphoid cells (ILC2s) play a key role in the initiation and maintenance of type 2 immune responses. The prostaglandin (PG) D₂-chemoattractant receptor-homologous molecule expressed on T_H2 cells (CRTH2) receptor axis potently induces cytokine production and ILC2 migration.

OBJECTIVE

We set out to examine PG production in human ILC2s and the implications of such endogenous production on ILC2 function.

METHODS

The effects of the COX-1/2 inhibitor flurbiprofen, the hematopoietic prostaglandin D₂ synthase (HPGDS) inhibitor KMN698, and the CRTH2 antagonist CAY10471 on human ILC2s were determined by assessing receptor and transcription factor expression, cytokine production, and gene expression with flow cytometry, ELISA, and quantitative RT-PCR, respectively. Concentrations of lipid mediators were measured by using liquid chromatography-tandem mass spectrometry and ELISA.

RESULTS

We show that ILC2s constitutively express HPGDS and upregulate COX-2 upon IL-2, IL-25, and IL-33 plus thymic stromal lymphopoietin stimulation. Consequently, PGD₂ and its metabolites can be detected in ILC2 supernatants. We reveal that endogenously produced PGD₂ is essential in cytokine-induced ILC2 activation because blocking of the COX-1/2 or HPGDS enzymes or the CRTH2 receptor abolishes ILC2 responses.

CONCLUSION

PGD₂ produced by ILC2s is, in a paracrine/autocrine manner, essential in cytokine-induced ILC2 activation. Hence we provide the detailed mechanism behind how CRTH2 antagonists represent promising therapeutic tools for allergic diseases by controlling ILC2 function.

Prostaglandin D2 receptor antagonists in allergic disorders: safety, efficacy, and future perspectives

INTRODUCTION

Prostaglandin D₂ (PGD₂) is a major cyclooxygenase mediator that is synthesized by activated human mast cells and other immune cells. The biological effects of PGD₂ are mediated by D-prostanoid (DP₁), DP₂ (CRTH2) and thromboxane prostanoid (TP) receptors that are expressed on several immune and non-immune cells involved in allergic inflammation. PGD₂ exerts various proinflammatory effects relevant to the pathophysiology of allergic disorders. Several selective, orally active, DP₂ receptor antagonists and a small number of DP₁ receptor antagonists are being developed for the treatment of allergic disorders.

AREAS COVERED

The role of DP₂ and DP₁ receptor antagonists in the treatment of asthma and allergic rhinitis.

EXPERT OPINION

Head-to-head studies that compare DP₁ antagonists with the standard treatment for allergic rhinitis are necessary to verify the role of these novel drugs as mono- or combination therapies. Further clinical trials are necessary to verify whether DP₂ antagonists as monotherapies or, more likely, as add-on therapies, will be effective for the treatment of different phenotypes of adult and childhood asthma. Long-term studies are necessary to evaluate the safety of targeted anti-PGD₂ treatments.

Activation of Th2 cells downregulates CRTh2 through an NFAT1 mediated mechanism

CRTh2 (encoded by PTGDR2) is a G-protein coupled receptor expressed by Th2 cells as well as eosinophils, basophils and innate lymphoid cells (ILC)2s. Activation of CRTh2, by its ligand prostaglandin (PG)D2, mediates production of type 2 cytokines (IL-4, IL-5 and IL-13), chemotaxis and inhibition of apoptosis. As such, the PGD2-CRTh2 pathway is considered important to the development and maintenance of allergic inflammation. Expression of CRTh2 is mediated by the transcription factor GATA3 during Th2 cell differentiation and within ILC2s. Other than this, relatively little is known regarding the cellular and molecular mechanisms regulating expression of CRTh2. Here, we show using primary human Th2 cells that activation (24hrs) through TCR crosslinking (αCD3/αCD28) reduced expression of both mRNA and surface levels of CRTh2 assessed by flow cytometry and qRT-PCR. This effect took more than 4 hours and expression was recovered following removal of activation. EMSA analysis revealed that GATA3 and NFAT1 can bind independently to overlapping sites within a CRTh2 promoter probe. NFAT1 over-expression resulted in loss of GATA3-mediated CRTh2 promoter activity, while inhibition of NFAT using a peptide inhibitor (VIVIT) coincided with recovery of CRTh2 expression. Collectively these data indicate that expression of CRTh2 is regulated through the competitive action of GATA3 and NFAT1. Though prolonged activation led to NFAT1-mediated downregulation, CRTh2 was re-expressed when stimulus was removed suggesting this is a dynamic mechanism and may play a role in PGD2-CRTh2 mediated allergic inflammation.

Inhibition of CRTH2-mediated Th2 activation attenuates pulmonary hypertension in mice

Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by progressive pulmonary artery (PA) remodeling. T helper 2 cell (Th2) immune response is involved in PA remodeling during PAH progression. Here, we found that CRTH2 (chemoattractant receptor homologous molecule expressed on Th2 cell) expression was up-regulated in circulating CD3⁺CD4⁺ T cells in patients with idiopathic PAH and in rodent PAH models. CRTH2 disruption dramatically ameliorated PA remodeling and pulmonary hypertension in different PAH mouse models. CRTH2 deficiency suppressed Th2 activation, including IL-4 and IL-13 secretion. Both CRTH2^+/+ bone marrow reconstitution and CRTH2^+/+ CD4⁺ T cell adoptive transfer deteriorated hypoxia + ovalbumin-induced PAH in CRTH2^-/- mice, which was reversed by dual neutralization of IL-4 and IL-13. CRTH2 inhibition alleviated established PAH in mice by repressing Th2 activity. In culture, CRTH2 activation in Th2 cells promoted pulmonary arterial smooth muscle cell proliferation through activation of STAT6. These results demonstrate the critical role of CRTH2-mediated Th2 response in PAH pathogenesis and highlight the CRTH2 receptor as a potential therapeutic target for PAH.

Targeting the PGD2/CRTH2/DP1 Signaling Pathway in Asthma and Allergic Disease: Current Status and Future Perspectives

Prostaglandin D₂ (PGD₂) released by degranulating mast cells is believed to play a key role in orchestrating mechanisms of inflammation in allergies and asthma. The biological effects of PGD₂ are mediated by D-prostanoid (DP1), CRTH2 (DP2), and thromboxane prostanoid (TP) receptors. The CRTH2 receptor is involved in induction of migration and activation of T helper type 2 (Th₂) lymphocytes, eosinophils, and basophils; up-regulation of adhesion molecules; and promotion of pro-inflammatory Th₂-type cytokines (interleukin [IL]-4, 5, 13), whereas the DP receptor is associated with relaxation of smooth muscles, vasodilation, inhibition of cell migration, and apoptosis of eosinophils. A number of CRTH2/PGD₂ receptor antagonists have been investigated in asthma and allergic diseases. The CRTH2 antagonist (OC000459) or dual CRTH2 and TP receptor antagonist (ramatroban) were effective in reducing eosinophilia, nasal mucosal swelling, and clinical symptoms of allergic rhinitis, with the latter drug registered for clinical use in this indication. OC000459 and setipiprant reduced the late but not early phase of response in an allergen challenge in atopic asthmatics. In persistent asthma, some molecules induced limited improvement in lung function, quality of life, and asthma symptoms (OC000459, BI671800), but in other trials with AMG 853 and AZ1981 these findings were not confirmed. The clear discrepancy between animal studies and clinical efficacy of CRTH2 antagonism in allergic rhinitis, and lack of efficacy in a general cohort of asthmatics, highlight the issue of patient phenotyping. There is no doubt that the PGD₂/CATH2/DP1 pathway plays a key role in allergic inflammation and further studies with selective or combined antagonisms in well defined cohorts of patients are needed.

Efficacy and safety of setipiprant in seasonal allergic rhinitis: results from Phase 2 and Phase 3 randomized, double-blind, placebo- and active-referenced studies

Background

Antagonism of chemoattractant receptor-homologous molecule on T-helper type-2 cells (CRTH2), a G-protein coupled receptor for prostaglandin D2, could be beneficial for treating allergic disorders. We present findings on the efficacy and safety/tolerability of a CRTH2 antagonist (setipiprant) in participants with seasonal allergic rhinitis (AR) in a real-life setting over 2 weeks.

Methods

A Phase 2 trial and a Phase 3 trial were conducted at seven centers in Texas, USA during the Mountain Cedar pollen season. Both were prospective, randomized, double-blind, placebo- and active-referenced (cetirizine) studies. The Phase 2 trial assessed setipiprant 100–1000 mg b.i.d. and 1000 mg o.d. versus placebo in adult and elderly participants. The Phase 3 trial assessed setipiprant 1000 mg b.i.d. in adolescent, adult, and elderly participants. Efficacy was assessed using daytime nasal symptom scores (DNSS), night-time nasal symptom scores (NNSS) and daytime eye symptom scores (DESS).

Results

579 participants were randomized in the Phase 2 trial (mean age 41.6–43.4 years); 630 were randomized in the Phase 3 trial (mean age 37.5–40.7 years). A statistically significant, dose-related improvement in mean change from baseline DNSS was observed over 2 weeks with setipiprant 1000 mg b.i.d. versus placebo in the Phase 2 trial (−0.15 [95% CI −0.29, −0.01]; p = 0.030). Setipiprant 1000 mg b.i.d. had no significant effect on this endpoint in the Phase 3 trial (−0.02 [95% CI −0.12, 0.07]; p = 0.652). Total and individual NNSS and DESS symptom scores were significantly improved with setipiprant 1000 mg b.i.d. versus placebo in the Phase 2 but not the Phase 3 trial. Setipiprant showed a favorable safety/tolerability profile.

Conclusions

The Phase 2 trial was the first large clinical study to assess a CRTH2 antagonist in seasonal AR in a real-life setting. Setipiprant dose-related efficacy in the Phase 2 trial was not confirmed during Phase 3. Setipiprant was well tolerated in both studies.

Trial registration NCT01241214 and NCT01484119

Electronic supplementary material

The online version of this article (doi:10.1186/s13223-017-0183-z) contains supplementary material, which is available to authorized users.

Two Phase II randomized trials on the CRTh2 antagonist AZD1981 in adults with asthma

Background

Chemoattractant receptor-homologous molecule expressed on T helper type 2 (Th2) cell (CRTh2) receptor antagonists is being investigated for asthma.

Objectives

The aim of this study was to assess the effects of the CRTh2 receptor antagonist, AZD1981 (with/without inhaled corticosteroids [ICSs]), on lung function and asthma control.

Patients and methods

Adults aged 18–60 years were enrolled in two randomized, placebo-controlled, parallel-group trials (protocol number: D9830C00003 [study 1, n=209] and protocol number: D9830C00004 [study 2, n=510]). In study 1, patients with stable asthma (forced expiratory volume in 1 second [FEV₁]: 65%−110%) were withdrawn from ICS (<400 µg/d) and randomized to AZD1981 1,000 mg twice daily (bid) or placebo. In study 2, patients with uncontrolled asthma (FEV₁: 40%−85%) despite ICS therapy (≥500 µg/d) were randomized to 50 mg, 400 mg, or 1,000 mg bid AZD1981 or placebo. The primary efficacy variable for both trials was the change in morning peak expiratory flow after 4 weeks of treatment. Secondary variables included Asthma Control Questionnaire (ACQ-5) scores, FEV₁ assessments, safety, and tolerability. In study 2, efficacy was also assessed according to atopic status.

Results

Following 4 weeks of treatment, there was a nonsignificant increase in morning peak expiratory flow on AZD1981 1,000 mg bid (9.5 L/min vs placebo, P=0.086 [study 1] and 12 L/min vs placebo, P=0.16 [study 2]). In study 2, all doses of AZD1981 provided significant improvements in ACQ-5 scores (0.26–0.3 units vs placebo, P=0.010–0.022); however, there was no dose–response relationship. Improved ACQ-5 scores and FEV₁ were observed in the majority of atopic patients treated with AZD1981. AZD1981 was well tolerated across treatment groups.

Conclusion

Further research may be warranted in atopic patients to fully evaluate the clinical efficacy of AZD1981.

Fevipiprant (QAW039), a Slowly Dissociating CRTh2 Antagonist with the Potential for Improved Clinical Efficacy

Here we describe the pharmacologic properties of a series of clinically relevant chemoattractant receptor-homologous molecules expressed on T-helper type 2 (CRTh2) receptor antagonists, including fevipiprant (NVP-QAW039 or QAW039), which is currently in development for the treatment of allergic diseases. [(3)H]-QAW039 displayed high affinity for the human CRTh2 receptor (1.14 ± 0.44 nM) expressed in Chinese hamster ovary cells, the binding being reversible and competitive with the native agonist prostaglandin D2(PGD2). The binding kinetics of QAW039 determined directly using [(3)H]-QAW039 revealed mean kinetic on (kon) and off (koff) values for QAW039 of 4.5 × 10(7)M(-1)min(-1)and 0.048 minute(-1), respectively. Importantly, thekoffof QAW039 (half-life = 14.4 minutes) was >7-fold slower than the slowest reference compound tested, AZD-1981. In functional studies, QAW039 behaved as an insurmountable antagonist of PGD2-stimulated [(35)S]-GTPγS activation, and its effects were not fully reversed by increasing concentrations of PGD2after an initial 15-minute incubation period. This behavior is consistent with its relatively slow dissociation from the human CRTh2 receptor. In contrast for the other ligands tested this time-dependent effect on maximal stimulation was fully reversed by the 15-minute time point, whereas QAW039's effects persisted for >180 minutes. All CRTh2 antagonists tested inhibited PGD2-stimulated human eosinophil shape change, but importantly QAW039 retained its potency in the whole-blood shape-change assay relative to the isolated shape change assay, potentially reflective of its relatively slower off rate from the CRTh2 receptor. QAW039 was also a potent inhibitor of PGD2-induced cytokine release in human Th2 cells. Slow CRTh2 antagonist dissociation could provide increased receptor coverage in the face of pathologic PGD2concentrations, which may be clinically relevant.

Heightened response of eosinophilic asthmatic patients to the CRTH2 antagonist OC000459

BACKGROUND

The CRTH2 antagonist OC000459 has previously been demonstrated to reduce airway inflammation and improve lung function in moderate persistent asthma. A study was conducted to determine the effect of lower once daily doses of OC000459 and to define the phenotype of subjects most responsive to treatment.

METHODS

Adult subjects (percentage of predicted forced expiratory volume in 1 s (FEV1 ) 60-85%) were randomized to OC000459 at three dose levels (25 mg once daily, 200 mg once daily or 100 mg twice daily) or placebo for 12 weeks (n = 117-125 per group, full analysis set). The primary endpoint was the change from baseline in prebronchodilator FEV1 , and secondary endpoints included Asthma Control Questionnaire (ACQ) and Standardised Asthma Quality of Life Questionnaire [AQLQ(S)], and incidence of exacerbations and respiratory tract infections.

RESULTS

OC459 caused a significant improvement in FEV1 compared with placebo at a dose of 25 mg once daily (P = 0.028). A similar increase was observed in the other dose groups, and the mean change in FEV1 in the pooled dose groups at endpoint was 95 ml greater than placebo (P = 0.024). In a post hoc analysis of atopic eosinophilic subjects with uncontrolled asthma, a mean increase in FEV1 of 220 ml was observed compared with placebo (P = 0.005). The mean increase in FEV1 was more marked in younger subjects in this group: for subjects aged ≤40 years, there was a mean increase of 355 ml compared with placebo (P = 0.007). Improvements in ACQ and AQLQ(S) were observed in both the full analysis set and the atopic eosinophilic subgroup. There was a lower incidence of exacerbations and respiratory infections in subjects treated with OC000459. There were no drug-related serious adverse events.

CONCLUSIONS

OC000459 is a safe and effective oral anti-inflammatory agent, which achieved clinically meaningful improvements in lung function and asthma control in allergic asthmatics with an eosinophil-dominant form of the disease. A dose of 25 mg given once daily was as effective as the higher doses studied.

Anti-inflammatory and antioxidant activities of Costus afer Ker Gawl. hexane leaf fraction in arthritic rat models

ETHNOPHARMACOLOGICAL RELEVANCE

Costus afer Ker Gawl is an indigenous tropical African medicinal plant used as therapy in the treatment of inflammatory ailments such as rheumatoid arthritis. This study was designed to evaluate the anti-inflammatory and antioxidant activities of the hexane fraction of C. afer leaves (CAHLF).

MATERIALS AND METHODS

The anti-inflammatory effect of varying doses of CAHLF on carrageenan, arachidonic acid, and formaldehyde induced arthritis in male albino rats׳ models were investigated in order to study the acute inflammatory phase. Complete Freund׳s Adjuvant (CFA)-induced arthritis model was used to study the chronic inflammatory phase. Two known anti-inflammatory drugs, Diclofenac sodium (non-steroidal anti-inflammatory drug [NSAID]) and prednisolone (glucocorticoid [steroidal drug]) were used as standards for comparison. Various biochemical indices viz. superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), reduced glutathione (GSH) and malondialdehyde (MDA), aspartate amino transferase (AST), alanine amino transferase (ALT), alkaline phosphatase (ALP), total bilirubin (TB), total protein (TP), globulin and albumin levels were assayed using spectrophotometric methods.

RESULTS

Control animals in which arthritis have been induced using carrageenan, arachidonic acid, formaldehyde or CFA showed significant increases (P<0.05) in paw edema when compared with normal animals. Treatment of the arthritis induced rats with CAHLF significantly (P<0.05) suppressed the edema. in vivo antioxidant study showed that CAHLF treated animals had a significantly (P<0.05) elevated GSH level, SOD, CAT and GST activities while MDA levels were significantly (P<0.05) reduced in the plasma, liver, kidney and brain. CAHLF treated rats had a significantly (P<0.05) reduced plasma AST, ALT and ALP. Plasma TP, globulin, TB levels were reduced while albumin levels were elevated in CAHLF treated animals.

CONCLUSIONS

CAHLF possesses substantial anti-inflammatory and antioxidant activities against inflammatory diseases especially arthritis. It could be considered as a choice candidate in pharmaceutical anti-inflammatory drug development.

Polyunsaturated Fatty Acid-derived lipid mediators and T cell function

Fatty acids are involved in T cell biology both as nutrients important for energy production as well as signaling molecules. In particular, polyunsaturated fatty acids are known to exhibit a range of immunomodulatory properties that progress through T cell mediated events, although the molecular mechanisms of these actions have not yet been fully elucidated. Some of these immune activities are linked to polyunsaturated fatty acid-induced alteration of the composition of cellular membranes and the consequent changes in signaling pathways linked to membrane raft-associated proteins. However, significant aspects of the polyunsaturated fatty acid bioactivities are mediated through their transformation to specific lipid mediators, products of cyclooxygenase, lipoxygenase, or cytochrome P450 enzymatic reactions. Resulting bioactive metabolites including prostaglandins, leukotrienes, and endocannabinoids are produced by and/or act upon T leukocytes through cell surface receptors and have been shown to alter T cell activation and differentiation, proliferation, cytokine production, motility, and homing events. Detailed appreciation of the mode of action of these lipids presents opportunities for the design and development of therapeutic strategies aimed at regulating T cell function.

Prostaglandin D2 activates group 2 innate lymphoid cells through chemoattractant receptor-homologous molecule expressed on TH2 cells

Background

Activation of the group 2 innate lymphoid cell (ILC2) population leads to production of the classical type 2 cytokines, thus promoting type 2 immunity. Chemoattractant receptor-homologous molecule expressed on T_H2 cells (CRTH2), a receptor for prostaglandin D₂ (PGD₂), is expressed by human ILC2s. However, the function of CRTH2 in these cells is unclear.

Objectives

We sought to determine the role of PGD₂ and CRTH2 in human ILC2s and compare it with that of the established ILC2 activators IL-25 and IL-33.

Methods

The effects of PGD₂, IL-25, and IL-33 on the cell migration, cytokine production, gene regulation, and receptor expression of ILC2s were measured with chemotaxis, ELISA, Luminex, flow cytometry, quantitative RT-PCR, and QuantiGene assays. The effects of PGD₂ under physiologic conditions were evaluated by using the supernatant from activated mast cells.

Results

PGD₂ binding to CRTH2 induced ILC2 migration and production of type 2 cytokines and many other cytokines. ILC2 activation through CRTH2 also upregulated the expression of IL-33 and IL-25 receptor subunits (ST2 and IL-17RA). The effects of PGD₂ on ILC2s could be mimicked by the supernatant from activated human mast cells and inhibited by a CRTH2 antagonist.

Conclusions

PGD₂ is an important and potent activator of ILC2s through CRTH2 mediating strong proallergic inflammatory responses. Through IgE-mediated mast cell degranulation, these innate cells can also contribute to adaptive type 2 immunity; thus CRTH2 bridges the innate and adaptive pathways in human ILC2s.

Biochemical and pharmacological characterization of AZD1981, an orally available selective DP2 antagonist in clinical development for asthma

BACKGROUND AND PURPOSE

The discovery of DP2 as a second receptor for PGD2 has prompted the search for antagonists as potential novel therapies based on the associations between PGD2 and disease. Here we describe the biochemical and pharmacological properties of 4-(acetylamino)-3-[(4-chlorophenyl)thio]-2-methyl-1H-indole-1-acetic acid (AZD1981), a novel DP2 receptor antagonist.

EXPERIMENTAL APPROACH

Binding to DP2 , functional receptor pharmacology and selectivity were studied in both human and animal systems.

KEY RESULTS

AZD1981 displaced radio-labelled PGD2 from human recombinant DP2 with high potency (pIC50 = 8.4). Binding was reversible, non-competitive and highly selective against a panel of more than 340 other enzymes and receptors, including DP1 (>1000-fold selective). AZD1981 inhibited DP2 -mediated shape change and CD11b up-regulation in human eosinophils, shape change in basophils and chemotaxis of human eosinophils and Th2 cells with similar potency. AZD1981 exhibited good cross-species binding activity against mouse, rat, guinea pig, rabbit and dog DP2 . Evaluation in mouse, rat or rabbit cell systems was not possible as they did not respond to DP2 agonists. Agonist responses were seen in guinea pig and dog, and AZD1981 blocked DP2 -mediated eosinophil shape change. Such responses were more robust in the guinea pig, where AZD1981 also blocked DP2 -dependent eosinophil emigration from bone marrow.

CONCLUSIONS AND IMPLICATIONS

AZD1981 is a DP2 antagonist that blocks functional responses in eosinophils, Th2 cells and basophils. It exhibited similar potency irrespective of the cell type, DP2 agonist or species used. This selective orally active agent is currently under clinical evaluation as a potential therapeutic agent in respiratory diseases including asthma.

Setipiprant, a selective oral antagonist of human CRTH2: relative bioavailability of a capsule and a tablet formulation in healthy female and male subjects

BACKGROUND

CRTH2 is a prostaglandin D2 receptor that plays an important role in allergic inflammation. Setipiprant is a potent CRTH2 antagonist under development for the treatment of allergic diseases.

OBJECTIVE

The aim of this study was to evaluate the tolerability and pharmacokinetics of a single oral dose of a setipiprant capsule (reference) and a tablet formulation.

METHODS

This was an open-label, 2-period, 2-way crossover, randomized study in which 20 healthy women and men (1:1 ratio) received either 2 250-mg capsules or a 500-mg tablet of setipiprant. Subjects were between 18 and 45 years old, with a body mass index of 18.0 to 28.0 kg/m(2). Differences in pharmacokinetics of setipiprant formulations were explored overall and by sex.

RESULTS

All subjects completed the study. Both formulations were well tolerated, with headache the most frequently reported adverse event (25% of subjects), followed by flatulence (15%) and somnolence and fatigue (10%). The adverse event profile in men and women and between formulations was similar. The ratios of geometric means for Cmax (0.94; 95% CI, 0.79-1.12) and AUC0-∞ (1.01; 95% CI, 0.92-1.12) were mostly within the limits of 0.80 to 1.25. When corrected for weight, the differences observed between sexes, within each treatment, for Cmax (capsules: 1.01; 95% CI, 0.71-1.44; tablet: 0.89; 95% CI, 0.62-1.26) and AUC0-∞ (capsules: 1.12; 95% CI, 0.86-1.47; tablet: 0.96; 95% CI, 0.73-1.25) were minor.

CONCLUSION

Both the setipiprant formulations were well tolerated. Setipiprant pharmacokinetics were similar between formulations, overall, and between sexes. The new tablet formulation may constitute a valid alternative to the capsule formulation for later clinical development phases. ClinicalTrials.gov identifier: NCT01877629.

Fish oil has beneficial effects on allergen-induced airway inflammation and hyperreactivity in mice

Background

Fish oil (FO) is rich in n-3 polyunsaturated fatty acids (PUFA), which have been suggested to be anti-inflammatory and are associated with improvement of several inflammatory diseases. In this study, we investigated the influence of FO on allergen-induced lung inflammation and airway hyperreactivity in mice.

Methods

Male A/J mice were fed either a standard-chow (SC) or a FO diet (FO) for 8 weeks. After 4 weeks, each group was further randomized for ovalbumin (SC-OVA and FO-OVA) or saline (SC-SAL and FO-SAL) challenge. Resistance and elastance were measured at baseline and after aerosolized methacholine, 24h after the last challenge. Bronchoalveolar lavage (BAL) was performed for leukocyte counts. Lung tissue mucus deposition, peribronchiolar matrix deposition and eosinophil infiltration were quantified. Serum immunoglobulin E (IgE) and IgG1 (ref 2.2), lung IL-4, IL-5, IL-10, IL-13, IL-17, INFγ and eotaxin-1 and 2 were detected by ELISA and nuclear factor kappa B (NFκB), GATA-3 and peroxisome proliferator-activated receptor gamma (PPARγ) expression was measured by Western blot.

Results

Levels of serum IgE and IgG1 were significantly higher in OVA sensitized mice. OVA challenge resulted in increased eosinophil infiltration, increased inflammatory cytokine production, peribronchiolar matrix and mucus deposition and airway hyperreactivity to aerosolized methacholine. Elevated lung NFκB and GATA-3 expression was noted in OVA-challenged mice. These changes were attenuated in mice fed with FO diet. Higher PPARγ expression was also detected in the lungs from the FO-fed groups.

Conclusion

Our results demonstrate that FO intake attenuated classical asthma features by suppressing the systemic sensitization, thus providing evidence that FO might be a prophylactic alternative for asthma prevention.

Proinflammatory and immunoregulatory roles of eicosanoids in T cells

Eicosanoids are inflammatory mediators primarily generated by hydrolysis of membrane phospholipids by phospholipase A2 to ω-3 and ω-6 C20 fatty acids that next are converted to leukotrienes (LTs), prostaglandins (PGs), prostacyclins (PCs), and thromboxanes (TXAs). The rate-limiting and tightly regulated lipoxygenases control synthesis of LTs while the equally well-controlled cyclooxygenases 1 and 2 generate prostanoids, including PGs, PCs, and TXAs. While many of the classical signs of inflammation such as redness, swelling, pain, and heat are caused by eicosanoid species with vasoactive, pyretic, and pain-inducing effects locally, some eicosanoids also regulate T cell functions. Here, we will review eicosanoid production in T cell subsets and the inflammatory and immunoregulatory functions of LTs, PGs, PCs, and TXAs in T cells.

The CRTH2 antagonist OC000459 reduces nasal and ocular symptoms in allergic subjects exposed to grass pollen, a randomised, placebo-controlled, double-blind trial

BACKGROUND

CRTH2 mediates activation of Th2 cells, eosinophils and basophils in response to prostaglandin D(2). The CRTH2 antagonist OC000459 has previously been demonstrated to reduce airway inflammation and improve lung function in moderate persistent asthma. The objective of the present study was to determine the involvement of CRTH2 in promoting nasal and ocular symptoms in allergic subjects exposed to grass pollen.

METHODS

A single centre, randomised, double-blind, placebo-controlled, two-way crossover study was conducted in 35 male subjects allergic to grass pollen comparing OC000459 200 mg bid with placebo for 8 days. Subjects were exposed to grass pollen (≥ 1400 grains/m(3)) for 6 h on the 2nd and 8th days of treatment and assessed for nasal symptoms, ocular symptoms, other symptoms, nasal secretion weight and rhinomanometry over the 6-h period. After a washout period of 3 weeks, subjects were switched to the alternative treatment for a further 8 days. The trial was registered on the clinical trials.gov database (Identifier NCT01448902).

RESULTS

During the first treatment period, treatment with OC000459 significantly reduced both nasal and ocular symptoms in allergic subjects compared with placebo after challenge with grass pollen. A significant effect was observed on the 2nd day of dosing which was increased on the 8th day of dosing. The therapeutic effects of OC000459 persisted into the second treatment period despite a 3-week washout phase. The safety profile of OC000459 was similar to that of placebo.

CONCLUSION

Treatment with OC000459 was well tolerated and led to a significant and persistent reduction in the symptoms of rhinoconjunctivitis.

Emerging drugs for asthma

INTRODUCTION

Current drug treatments for asthma relieve bronchospasm and airway inflammation but do not offer a cure, and symptoms return when treatment is stopped. Asthma management guidelines emphasize the importance of effective asthma treatment to achieve and maintain asthma control. However, despite widely available and effective treatments, achieving asthma control is still an unmet need for many patients.

AREAS COVERED

Remarkable efforts have been made to identify the characteristic features of difficult-to-control (usually severe) asthma that are different from those described for mild-to-moderate asthma, setting the stage for the development of new and even individualized therapies. The most fascinating options of the new asthma treatments are biologic therapies, in particular monoclonal antibodies. In addition, some novel once-daily combinations of long-acting β(2)-agonist and inhaled corticosteroids are under development.

EXPERT OPINION

Asthma is a complex syndrome made up of a number of disease variants or asthma phenotypes, with different underlying pathophysiology. As different drugs target different pathways, it is necessary to determine the individual profile of pathophysiological abnormalities for each patient. Several cytokines have been implicated in the inflammatory cascades leading to the different asthma phenotypes, and the most relevant ones are discussed. The challenge in treating asthma resides precisely in its heterogeneity.

Leukotriene E4 activates human Th2 cells for exaggerated proinflammatory cytokine production in response to prostaglandin D2

PGD(2) exerts a number of proinflammatory responses through a high-affinity interaction with chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2) and has been detected at high concentrations at sites of allergic inflammation. Because cysteinyl leukotrienes (cysLTs) are also produced during the allergic response, we investigated the possibility that cysLTs may modulate the response of human Th2 cells to PGD(2). PGD(2) induced concentration-dependent Th2 cytokine production in the absence of TCR stimulation. Leukotrienes D(4) and E(4) (LTE(4)) also stimulated the cytokine production but were much less active than PGD(2). However, when combined with PGD(2), cysLTs caused a greater than additive enhancement of the response, with LTE(4) being most effective in activating Th2 cells. LTE(4) enhanced calcium mobilization in response to PGD(2) in Th2 cells without affecting endogenous PGD(2) production or CRTH2 receptor expression. The effect of LTE(4) was inhibited by montelukast but not by the P2Y(12) antagonist methylthioadenosine 5'-monophosphate. The enhancing effect was also evident with endogenous cysLTs produced from immunologically activated mast cells because inhibition of cysLT action by montelukast or cysLT synthesis by MK886, an inhibitor of 5-lipoxygenase-activating protein, reduced the response of Th2 cells to the levels produced by PGD(2) alone. These findings reveal that cysLTs, in particular LTE(4), have a significant proinflammatory impact on T cells and demonstrate their effects on Th2 cells are mediated by a montelukast-sensitive receptor.

BLT2 Is upregulated in allergen-stimulated mast cells and mediates the synthesis of Th2 cytokines

Mast cells are effector cells that mediate the allergic response through Ag stimulation of IgE bound to FcεRI. In allergic reactions, cross-linking of the surface receptors for IgE on mast cells results in the synthesis of Th2 cytokines such as IL-4 and IL-13, which are critical for the initiation and progression of the allergic response. Despite the important roles of these cytokines, the signaling mechanism by which Ag stimulation mediates the production of IL-4 and IL-13 in mast cells is not clearly understood. In the present study, we found that Ag-stimulated bone marrow-derived mast cells (BMMCs) highly upregulated the expression of BLT2, a leukotriene B(4) receptor, and that blockade of BLT2 with the specific antagonist LY255283 or small interfering RNA knockdown completely abolished the production of Th2 cytokines. Furthermore, BMMCs overexpressing BLT2 showed significantly enhanced production of Th2 cytokines compared with wild-type BMMCs. Additionally, we found that the generation of Nox1-derived reactive oxygen species occurs downstream of BLT2, thus mediating the synthesis of Th2 cytokines. Taken together, our results suggest that the BLT2-Nox1-reactive oxygen species cascade is a previously unsuspected mediatory signaling mechanism to Th2 cytokine production in Ag-stimulated BMMCs, thus contributing to allergic response.

Mast cell-derived prostaglandin D2 controls hyaluronan synthesis in human orbital fibroblasts via DP1 activation: implications for thyroid eye disease

Thyroid eye disease (TED) is a debilitating disorder characterized by the accumulation of adipocytes and hyaluronan (HA). Production of HA by fibroblasts leads to remarkable increases in tissue volume and to the anterior displacement of the eyes. Prostaglandin D(2) (PGD(2)), mainly produced by mast cells, promotes orbital fibroblast adipogenesis. The mechanism by which PGD(2) influences orbital fibroblasts and their synthesis of HA is poorly understood. We report here that mast cell-derived PGD(2) is a key factor that promotes HA biosynthesis by orbital fibroblasts. Primary orbital fibroblasts from TED patients were isolated and used to test the effects of PGD(2), prostaglandin J(2), as well as prostaglandin D receptor (DP) agonists and antagonists on HA synthesis. The expression of HA synthase (HAS), hyaluronidase, DP1, and DP2 mRNA levels was assessed by PCR. Small interfering RNAs against HAS1 or HAS2 were used to assess the importance of HAS isoforms on HA production. Treatment of human orbital fibroblasts with PGD(2) and PGJ(2) increased HA synthesis and HAS mRNA. HAS2 was the dominant isoform responsible for HA production by PGD(2). The effect of PGD(2) on HA production was mimicked by the selective DP1 agonist BW245C. The DP1 antagonist MK-0524 completely blocked PGD(2)-induced HA synthesis. Human mast cells (HMC-1) produced PGD(2). Co-culture of HMC-1 cells with orbital fibroblasts induced HA production and inhibition of mast cell-derived PGD(2) prevented HA synthesis. Mast cell-derived PGD(2) increased HA production via activation of DP1. Selectively targeting the production of PGD(2) and/or activation of DP1 may prevent pathological changes associated with TED.

CRTH2 mediates the activation of human Th2 cells in response to PGD(2) released from IgE/anti-IgE treated nasal polyp tissue

BACKGROUND

Mast cells release mediators upon stimulation that contribute to the pathogenesis of chronic airway disease, including the recruitment and activation of Th2 lymphocytes. The objective was to determine the involvement of prostaglandin D(2) (PGD(2)) and its receptors in the chemotaxis of Th2 cells, using nasal polyp tissue.

METHODS

Tissue explants from ten patients with nasal polyposis were incubated with RPMI alone or RPMI containing IgE/anti-IgE for 30 min. Some samples were treated with diclofenac to inhibit the production of PGD(2). Supernatants were assayed for PGD(2) content and for their ability to promote human Th2 cell chemotaxis in the presence and absence of a CRTH2 antagonist. Transcript levels of D protanoid receptor type 1 (DP(1)), chemoattractant receptor-homologous receptor expressed on Th2 cells (CRTH2) and PGD(2) synthase were analysed by real time PCR.

RESULTS

Increased release of PGD(2) by nasal polyp tissue treated with IgE/anti-IgE was significantly inhibited by preincubation of the tissue with diclofenac. Transcript levels of PGD(2) synthase, DP(1) and CRTH2 receptors increased after stimulation with IgE/anti-IgE. Supernatants from IgE/anti-IgE-stimulated nasal polyp tissue caused significantly increased chemotaxis of Th2 cells. The levels of PGD(2) produced and the degree of Th2 cell chemotaxis were highly correlated. Diclofenac inhibited the production of Th2 cell chemotactic activity, and the chemotactic effect of the supernatant on Th2 cells was inhibited by the CRTH2 antagonist ramatroban.

CONCLUSION

These data suggest that in immunologically activated nasal polyp tissue, PGD(2) produced by mast cells promotes the migration of Th2 cells through a CRTH2 dependent mechanism.