Prostaglandin D2 (PGD2) and cysteinyl leukotrienes (cysLTs) are lipid mediators derived from mast cells, which activate TH2 cells. The combination of PGD2 and cysLTs (notably cysteinyl leukotriene E4 ...LTE4) enhances TH2 cytokine production. However, the synergistic interaction of cysLTs with PGD2 in promoting TH2 cell activation is still poorly understood. The receptors for these mediators are drug targets in the treatment of allergic diseases, and hence understanding their interaction is likely to have clinical implications.
We aimed to comprehensively define the roles of PGD2, LTE4, and their combination in activating human TH2 cells and how such activation might allow the TH2 cells to engage downstream effectors, such as neutrophils, which contribute to the pathology of allergic responses.
The effects of PGD2, LTE4, and their combination on human TH2 cell gene expression were defined by using a microarray, and changes in specific inflammatory pathways were confirmed by means of PCR array, quantitative RT-PCR, ELISA, Luminex, flow cytometry, and functional assays, including analysis of downstream neutrophil activation. Blockade of PGD2 and LTE4 was tested by using TM30089, an antagonist of chemoattractant receptor-homologous molecule expressed on TH2 cells, and montelukast, an antagonist of cysteinyl leukotriene receptor 1.
PGD2 and LTE4 altered the transcription of a wide range of genes and induced diverse functional responses in TH2 cells, including cell adhesion, migration, and survival and cytokine production. The combination of these lipids synergistically or additively enhanced TH2 responses and, strikingly, induced marked production of diverse nonclassical TH2 inflammatory mediators, including IL-22, IL-8, and GM-CSF, at concentrations sufficient to affect neutrophil activation.
PGD2 and LTE4 activate TH2 cells through different pathways but act synergistically to promote multiple downstream effector functions, including neutrophil migration and survival. Combined inhibition of both PGD2 and LTE4 pathways might provide an effective therapeutic strategy for allergic responses, particularly those involving interaction between TH2 cells and neutrophils, such as in patients with severe asthma.
D prostanoid receptor 2 (DP₂) also known as chemoattractant receptor-homologous molecule expressed on T helper 2 (Th2) cells (CRTH2) is selectively expressed by Th2 lymphocytes, eosinophils, and ...basophils and mediates recruitment and activation of these cell types in response to prostaglandin D₂ (PGD₂). (5-Fluoro-2-methyl-3-quinolin-2-ylmethylindo-1-yl)-acetic acid (OC000459) is an indole-acetic acid derivative that potently displaces ³HPGD₂ from human recombinant DP₂ (K(i) = 0.013 μM), rat recombinant DP₂ (K(i) = 0.003 μM), and human native DP₂ (Th2 cell membranes; K(i) = 0.004 μM) but does not interfere with the ligand binding properties or functional activities of other prostanoid receptors (prostaglandin E₁₋₄ receptors, D prostanoid receptor 1, thromboxane receptor, prostacyclin receptor, and prostaglandin F receptor). OC000459 inhibited chemotaxis (IC₅₀ = 0.028 μM) of human Th2 lymphocytes and cytokine production (IC₅₀ = 0.019 μM) by human Th2 lymphocytes. OC000459 competitively antagonized eosinophil shape change responses induced by PGD₂ in both isolated human leukocytes (pK(B) = 7.9) and human whole blood (pK(B) = 7.5) but did not inhibit responses to eotaxin, 5-oxo-eicosatetraenoic acid, or complement component C5a. OC000459 also inhibited the activation of Th2 cells and eosinophils in response to supernatants from IgE/anti-IgE-activated human mast cells. OC000459 had no significant inhibitory activity on a battery of 69 receptors and 19 enzymes including cyclooxygenase 1 (COX1) and COX2. OC000459 was found to be orally bioavailable in rats and effective in inhibiting blood eosinophilia induced by 13,14-dihydro-15-keto-PGD₂ (DK-PGD₂) in this species (ED₅₀ = 0.04 mg/kg p.o.) and airway eosinophilia in response to an aerosol of DK-PGD₂ in guinea pigs (ED₅₀ = 0.01 mg/kg p.o.). These data indicate that OC000459 is a potent, selective, and orally active DP₂ antagonist that retains activity in human whole blood and inhibits mast cell-dependent activation of both human Th2 lymphocytes and eosinophils.
Summary Activation of human CRTH2+ CD4+ T helper type 2 (Th2) cells with anti‐CD3/anti‐CD28 led to time‐dependent production of prostaglandin D2 (PGD2) which peaked at 8 hr. The production of PGD2 ...was completely inhibited by cotreatment with the cyclo‐oxygenase inhibitor diclofenac (10 μm) but was not affected by cotreatment with ramatroban, a dual antagonist of both the thromboxane‐like prostanoid (TP) receptor and the chemoattractant receptor‐homologous molecule expressed on Th2 cells (CRTH2). Supernatants from activated CRTH2+ CD4+ Th2 cells caused a concentration‐dependent increase in the migration of naive CRTH2+ CD4+ Th2 cells compared to supernatants from unstimulated CRTH2+ CD4+ Th2 cells. The level of chemotactic activity peaked at 8 hr after activation, corresponding to the peak levels of PGD2, but production of chemotactic activity was only partially inhibited by the cyclo‐oxygenase inhibitor diclofenac. In contrast, ramatroban completely inhibited the chemotactic responses of naive Th2 cells to supernatants from activated CRTH2+ CD4+ Th2 cells collected up to 8 hr after activation, although supernatants collected 24 hr after activation were less sensitive to inhibition by ramatroban. The selective TP antagonist SQ29548 did not inhibit migration of Th2 cells, implicating CRTH2 in this response. These data suggest that CRTH2 plays an important paracrine role in mediating chemotactic activation of Th2 cells. Interestingly, although PGD2 is produced from Th2 cells and contributes to this paracrine activation, it appears that additional CRTH2 agonist factors are also produced by activated Th2 cells and the production of these factors occurs independently of the cyclo‐oxygenase pathway of the arachidonic acid metabolism.
Background Prostaglandin D2(PGD2) and cysteinyl leukotrienes (cysLTs) are lipid mediators derived from mast cells, which activate TH2 cells. The combination of PGD2and cysLTs (notably cysteinyl ...leukotriene E4LTE4) enhances TH2 cytokine production. However, the synergistic interaction of cysLTs with PGD2in promoting TH2 cell activation is still poorly understood. The receptors for these mediators are drug targets in the treatment of allergic diseases, and hence understanding their interaction is likely to have clinical implications. Objective We aimed to comprehensively define the roles of PGD2, LTE4, and their combination in activating human TH2 cells and how such activation might allow the TH2 cells to engage downstream effectors, such as neutrophils, which contribute to the pathology of allergic responses. Methods The effects of PGD2, LTE4, and their combination on human TH2 cell gene expression were defined by using a microarray, and changes in specific inflammatory pathways were confirmed by means of PCR array, quantitative RT-PCR, ELISA, Luminex, flow cytometry, and functional assays, including analysis of downstream neutrophil activation. Blockade of PGD2and LTE4was tested by using TM30089, an antagonist of chemoattractant receptor-homologous molecule expressed on TH2 cells, and montelukast, an antagonist of cysteinyl leukotriene receptor 1. Results PGD2and LTE4altered the transcription of a wide range of genes and induced diverse functional responses in TH2 cells, including cell adhesion, migration, and survival and cytokine production. The combination of these lipids synergistically or additively enhanced TH2 responses and, strikingly, induced marked production of diverse nonclassical TH2 inflammatory mediators, including IL-22, IL-8, and GM-CSF, at concentrations sufficient to affect neutrophil activation. Conclusions PGD2and LTE4activate TH2 cells through different pathways but act synergistically to promote multiple downstream effector functions, including neutrophil migration and survival. Combined inhibition of both PGD2and LTE4pathways might provide an effective therapeutic strategy for allergic responses, particularly those involving interaction between TH2 cells and neutrophils, such as in patients with severe asthma.
Background Prostaglandin D2 (PGD2 ) and cysteinyl leukotrienes (cysLTs) are lipid mediators derived from mast cells, which activate TH 2 cells. The combination of PGD2 and cysLTs (notably cysteinyl ...leukotriene E4 LTE4 ) enhances TH 2 cytokine production. However, the synergistic interaction of cysLTs with PGD2 in promoting TH 2 cell activation is still poorly understood. The receptors for these mediators are drug targets in the treatment of allergic diseases, and hence understanding their interaction is likely to have clinical implications. Objective We aimed to comprehensively define the roles of PGD2 , LTE4 , and their combination in activating human TH 2 cells and how such activation might allow the TH 2 cells to engage downstream effectors, such as neutrophils, which contribute to the pathology of allergic responses. Methods The effects of PGD2 , LTE4 , and their combination on human TH 2 cell gene expression were defined by using a microarray, and changes in specific inflammatory pathways were confirmed by means of PCR array, quantitative RT-PCR, ELISA, Luminex, flow cytometry, and functional assays, including analysis of downstream neutrophil activation. Blockade of PGD2 and LTE4 was tested by using TM30089, an antagonist of chemoattractant receptor-homologous molecule expressed on TH 2 cells, and montelukast, an antagonist of cysteinyl leukotriene receptor 1. Results PGD2 and LTE4 altered the transcription of a wide range of genes and induced diverse functional responses in TH 2 cells, including cell adhesion, migration, and survival and cytokine production. The combination of these lipids synergistically or additively enhanced TH 2 responses and, strikingly, induced marked production of diverse nonclassical TH 2 inflammatory mediators, including IL-22, IL-8, and GM-CSF, at concentrations sufficient to affect neutrophil activation. Conclusions PGD2 and LTE4 activate TH 2 cells through different pathways but act synergistically to promote multiple downstream effector functions, including neutrophil migration and survival. Combined inhibition of both PGD2 and LTE4 pathways might provide an effective therapeutic strategy for allergic responses, particularly those involving interaction between TH 2 cells and neutrophils, such as in patients with severe asthma.
Activation of human CRTH2 super(+) CD4 super(+) T helper type 2 (Th2) cells with anti-CD3anti-CD28 led to time-dependent production of prostaglandin D sub(2) (PGD sub(2)) which peaked at 8 hr. The ...production of PGD sub(2) was completely inhibited by cotreatment with the cyclo-oxygenase inhibitor diclofenac (10 mu m) but was not affected by cotreatment with ramatroban, a dual antagonist of both the thromboxane-like prostanoid (TP) receptor and the chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2). Supernatants from activated CRTH2 super(+) CD4 super(+) Th2 cells caused a concentration-dependent increase in the migration of naive CRTH2 super(+) CD4 super(+) Th2 cells compared to supernatants from unstimulated CRTH2 super(+) CD4 super(+) Th2 cells. The level of chemotactic activity peaked at 8 hr after activation, corresponding to the peak levels of PGD sub(2), but production of chemotactic activity was only partially inhibited by the cyclo-oxygenase inhibitor diclofenac. In contrast, ramatroban completely inhibited the chemotactic responses of naive Th2 cells to supernatants from activated CRTH2 super(+) CD4 super(+) Th2 cells collected up to 8 hr after activation, although supernatants collected 24 hr after activation were less sensitive to inhibition by ramatroban. The selective TP antagonist SQ29548 did not inhibit migration of Th2 cells, implicating CRTH2 in this response. These data suggest that CRTH2 plays an important paracrine role in mediating chemotactic activation of Th2 cells. Interestingly, although PGD sub(2) is produced from Th2 cells and contributes to this paracrine activation, it appears that additional CRTH2 agonist factors are also produced by activated Th2 cells and the production of these factors occurs independently of the cyclo-oxygenase pathway of the arachidonic acid metabolism.
CRTH2 (chemoattractant receptor expressed on T-helper (Th) type 2 cells) is a G-protein-coupled receptor expressed by Th2 lymphocytes and eosinophils that mediates prostaglandin (PG)D(2)-driven ...chemotaxis. We studied the efficacy of the oral CRTH2 antagonist OC000459 in steroid-naïve asthmatic patients. A randomised, double-blind, placebo-controlled, two-way crossover study of 16 days' treatment with OC000459 (200 mg twice daily) on the late (LAR) and early (EAR) asthmatic responses to bronchial allergen challenge was conducted, with 16 subjects completing the study. There was a 25.4% (95% CI 5.1-45.6%) reduction in the LAR area under the curve (AUC) for change in forced expiratory volume in 1 s with OC000459 compared with placebo (p=0.018) but no effect on the EAR. Sputum eosinophil counts at 1 day post-allergen challenge were lower after OC000459 treatment (p=0.002). PGD(2)-induced blood eosinophil shape change ex vivo was assessed at day 7 (n=7). The AUC of eosinophil shift for OC000459 was lower than placebo; the mean difference was -33.6% (95% CI -66.8- -0.4%; p=0.048). OC000459 treatment inhibited LAR and post-allergen increase in sputum eosinophils. This CRTH2 antagonist appears to inhibit allergic inflammation in asthma.
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