Prostaglandin D₂ Induces IL-8 and GM-CSF by Bronchial Epithelial Cells in a CRTH2-Independent Pathway

Abstract

Background: Prostaglandin D₂ (PGD₂), a major prostanoid produced by activated mast cells, has long been implicated in allergic diseases. PGD₂ demonstrates its effects through two G-protein-coupled receptors, DP and CRTH2. The PGD₂/CRTH2 system mediates chemotaxis of eosinophils, basophils, and Th2 cells, which are involved in the induction of allergic inflammation. Although recent studies have shown that the specific receptors for PGD₂, DP, and CRTH2 are expressed in various human tissues, the role of PGD₂ is unknown in human bronchial epithelial cells. In this study, we investigated the expression and function of CRTH2/DP on NCI-H₂₉₂ and NHBE cells. Method: The CRTH2/DP expression was examined by RT-PCR and flow-cytometric analysis. NCI-H₂₉₂ and NHBE cells were cultured in the presence of various stimulants. The resulting supernatants were measured by ELISA. Results: We demonstrated that PGD₂ induced production of IL-8 and GM-CSF in NCI-H₂₉₂ and NHBE cells. DK-PGD₂ (CRTH2 agonist) and latanoprost (FP, a prostaglandin F receptor, agonist) failed to augment the production of these cytokines. Pretreatment with ramatroban (CRTH2 antagonist) and AL8810 (FP antagonist) did not reduce the production of these cytokines. The PGD₂-induced cytokine production was inhibited by pertussis toxin or specific inhibitors for MAP/ERK kinase (PD98059) and p38 MAP kinase (SB202190). Conclusion: These results suggest that PGD₂ is a potent inducer of IL-8 and GM-CSF production with MAP/ERK and p38 MAP kinase activation, but this is independent of CRTH2 activation.

Possible Novel Receptor for PGD₂ on Human Bronchial Epithelial Cells

“…Therefore, to find out whether DP is expressed on NCI-H 292 and NHBE, we used RT-PCR and flow-cytometric analysis for our examinations. DP mRNA and protein were not detected in these cells [13]. In support of our findings, Boie et al [9] reported that DP was not detected in human lung using Northern blot analysis.…”

“…It is of paramount interest to investigate the mechanism of IL-8 and GM-CSF production from epithelial cells. We found that the production of IL-8 and GM-CSF was observed in bronchial epithelial cells stimulated with PGD 2 in a dose-dependent manner, and revealed a significant correlation between IL-8 and GM-CSF production [13]. Consistent with these results, PGD 2 accelerates Th2 type and eosinophilic inflammation by induction of cytokines and chemokines as shown in figure 1.…”

“…We found CRTH2 expression on NCI-H 292 and NHBE cells. CRTH2 mRNA and protein with an inner cell but no cell surface were detectable in NCI-H 292 and NHBE [13]. This finding leads us to speculate that intracellular expression of CRTH2 on the epithelial cell has some functional potential, and indicated that further research is needed.…”

Pharmacological Blockade of the DP2 Receptor Inhibits Cigarette Smoke-Induced Inflammation, Mucus Cell Metaplasia, and Epithelial Hyperplasia in the Mouse Lung

“…While this manuscript was in preparation, similar results were reported with the selective DP2 antagonist AZ11805131 (Sargent et al, 2009). The epithelial cell acts as a first line of defense against harmful components in cigarette smoke, and DP2 is expressed on human bronchial epithelial cells (Chiba et al, 2006;Sargent et al, 2009). Intracellular expression of DP2 was demonstrated in NCI-H292 and normal human bronchial epithelial cells by both reverse transcription-polymerase chain reaction and flow cytometry (Chiba et al, 2007).…”

Prostaglandins but not leukotrienes alter extracellular matrix protein deposition and cytokine release in primary human airway smooth muscle cells and fibroblasts

“…Very few studies have examined these effects in respiratory cell types. Of the few studies that exist, Tavakoli et al (63) showed that PGE 2 induced IL-6, Chiba et al (12) showed that PGD 2 induced IL-8 in human bronchial epithelial cells, and Ammit et al (3) showed that PGE 2 increased IL-6 in …”