Author Affiliations: Research Center for Inflammation and Regenerative Medicine, Faculty of Life and Medical Sciences, Doshisha University (Dr Ueta) and Department of Ophthalmology, Kyoto Prefectural University of Medicine (Drs Ueta, Sotozono, Yokoi, and Kinoshita), Kyoto, Japan.
Elsewhere, we reported that in the tears and serum of patients with acute-stage Stevens-Johnson syndrome or toxic epidermal necrolysis, the levels of interleukin 6 (IL-6), IL-8, and monocyte chemoattractant protein 1 (MCP-1) were dramatically increased.1 We also reported that Stevens-Johnson syndrome or toxic epidermal necrolysis with severe ocular complications was associated with polymorphism of the prostaglandin E receptor 3 (EP3) gene (PTGER3).2
Prostanoids are a group of lipid mediators that form in response to various stimuli. They include prostaglandin D2 (PGD2), PGE2, PGF2α, PGI2, and thromboxane A2. There are 4 subtypes of the PGE receptor: EP1, EP2, EP3, and EP4. We previously reported that PGE2 suppresses polyinosine–polycytidylic acid (polyI:C)–stimulated cytokine production via EP2 and/or EP3 in human ocular surface epithelial cells.3,4 PolyI:C is a ligand of Toll-like receptor 3, which is strongly expressed in ocular surface epithelium.5 We found that PGE2 suppresses the production of IL-6, chemokine (C-X-C motif) ligand 10, chemokine (C-X-C motif) ligand 11, and chemokine (C-C motif) ligand 5 but not IL-8 by epithelial cells on the human ocular surface3; it remains to be determined whether it also suppresses MCP-1 production. Monocyte chemoattractant protein 1 plays a significant role in the recruitment of monocytes and lymphocytes to the site of cellular immune reactions. In this study, we investigated whether PGE 2 downregulates polyI:C-induced MCP-1 production.
All experiments were conducted in accordance with the principles set forth in the Declaration of Helsinki. Enzyme-linked immunosorbent assay and quantitative real-time polymerase chain reaction were performed with primary human conjunctival epithelial cells and immortalized human corneal-limbal epithelial cells using previously described methods (eAppendix).3
First, we examined whether PGE2 downregulated the production and messenger RNA (mRNA) expression of MCP-1 induced by polyI:C stimulation in human conjunctival and corneal epithelial cells. We found that it significantly attenuated the production of MCP-1 (Figure, A). Quantitative real-time polymerase chain reaction confirmed that the mRNA expression of MCP-1 was significantly downregulated by PGE2 (Figure, A).
Figure. Prostaglandin E2 (PGE2) attenuated the messenger RNA (mRNA) expression and production of monocyte chemoattractant protein 1 via both prostaglandin E receptor 2 (EP2) and EP3. A, Primary human conjunctival epithelial cells (PHCjE) and human corneal-limbal epithelial cells (HCLE) were exposed to 10 μg/mL of polyinosine–polycytidylic acid (polyI:C) and 100 μg/mL of PGE2 for 24 hours (enzyme-linked immunosorbent assay) or 6 hours (quantitative real-time polymerase chain reaction). GAPDH indicates glyceraldehyde-3-phosphate dehydrogenase. B and C, The PHCjE and HCLE were exposed to 10 μg/mL of polyI:C and 10 μg/mL of the EP2, EP3, or EP4 agonist for 24 hours (enzyme-linked immunosorbent assay) (B) or 6 hours (quantitative real-time polymerase chain reaction) (C). Data are representative of 3 separate experiments and are given as the mean (SEM) from 1 experiment carried out in 6 to 8 wells (enzyme-linked immunosorbent assay) (B) or 4 to 6 wells (quantitative real-time polymerase chain reaction) (C) per group. * P < .05; † P < .005; ‡ P < .001.
Next, we examined which PGE2 receptor(s) contributed to the downregulation of polyI:C-induced MCP-1. We used the EP2 agonist ONO-AE-259, the EP3 agonist ONO-AE-248, and the EP4 agonist ONO-AE-329. Enzyme-linked immunosorbent assay showed that the EP2 and EP3 agonists significantly suppressed the polyI:C-induced production of MCP-1, while the EP4 agonist did not exert suppression (Figure, B). Quantitative real-time polymerase chain reaction confirmed that the EP2 and EP3 agonists significantly downregulated the mRNA expression of MCP-1 (Figure, C). Thus, our results document that PGE2 attenuated the mRNA expression and production of MCP-1 via both EP2 and EP3.
In human macrophages, PGE2 attenuated the lipopolysaccharide-induced mRNA and protein expression of chemokines including MCP-1 through EP4.6 On the other hand, we demonstrated that in human ocular surface epithelial cells, PGE2 attenuated the polyI:C-induced mRNA and protein expression of MCP-1 through EP2 and EP3 but not EP4. Our findings suggest that EP2 and EP3 play important roles in the regulation of inflammation in epithelial cells, while EP2 and EP4 have important roles in immune cells such as macrophages.
In the tears and serum of patients with acute-stage Stevens-Johnson syndrome or toxic epidermal necrolysis, the levels of IL-6, IL-8, and MCP-1 were dramatically increased.1 Although IL-8 was not regulated by PGE2, IL-6 was regulated by PGE2 via EP3 in human ocular surface epithelial cells.3 Herein, we demonstrated that MCP-1 could be regulated by PGE2 via EP2 and EP3. The regulation of cytokine production by PGE2 may be associated with the pathogenesis of Stevens-Johnson syndrome or toxic epidermal necrolysis with severe ocular complications because it was associated with polymorphism of the EP3 gene (PTGER3), one of the PGE receptors (EP1, EP2, EP3, EP4).2
In summary, our results show that MCP-1 produced by human ocular surface epithelial cells could be downregulated by PGE2 via EP2 and EP3.
Correspondence: Dr Ueta, Department of Ophthalmology, Kyoto Prefectural University of Medicine, 465 Kajiicho, Hirokoji, Kawaramachi, Kamigyoku, Kyoto 602-0841, Japan (email@example.com).
Author Contributions: Dr Ueta had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Financial Disclosure: The work described in this article was carried out in collaboration with Ono Pharmaceutical Co Ltd, who supplied ONO-AE-248 used in this study.
Funding/Support: This work was supported in part by grants-in-aid for scientific research from the Japanese Ministry of Health, Labour, and Welfare, the Japanese Ministry of Education, Culture, Sports, Science, and Technology, the Kyoto Foundation for the Promotion of Medical Science, the National Institute of Biomedical Innovation of Japan, the Intramural Research Fund of Kyoto Prefectural University of Medicine, and the Shimizu Foundation for Immunological Research Grant.
Additional Contributions: Chikako Endo provided technical assistance.
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