Effect of Prostaglandin I2 Analogs on Cytokine Expression in Human Myeloid Dendritic Cells via Epigenetic Regulation

Chang-Hung Kuo,Hsiu-Lin Chen,Ya-Ling Hsu,Yi-Pin Chen,Po-Lin Kuo,Wan-Ju Wei,Yuh-Jyh Jong,Ching-Hsiung Lin,San-Nan Yang,Chih-Hsing Hung,Shau-Ku Huang,Ming-Yii Huang

doi:10.2119/molmed.2011.00193

Abstract

Prostaglandin I(2) (PGI(2)) analog is regarded as a potential candidate for treating asthma. Human myeloid dendritic cells (mDCs) play a critical role in the pathogenesis of asthma. However, the effects of PGI(2) analog on human mDCs are unknown. In the present study, circulating mDCs were isolated from six healthy subjects. The effects of PGI(2) analogs iloprost and treprostinil on cytokine production, maturation and T-cell stimulatory function of human mDCs were investigated. Tumor necrosis factor (TNF)-α and interleukin (IL)-10 were measured by enzyme-linked immunosorbent assay. The expression of costimulatory molecules was investigated by flow cytometry. T-cell stimulatory function was investigated by measuring interferon (IFN)-γ, IL-13 and IL-10 production by T cells cocultured with iloprost-treated mDCs. Intracellular signaling was investigated by Western blot and chromatin immunoprecipitation. We found that iloprost and treprostinil induced IL-10, but suppressed TNF-α production in polyinosinic-polycytidylic acid (poly I:C)-stimulated mDCs. This effect was reversed by the I-prostanoid (IP), E-prostanoid (EP) receptor antagonists or intracellular free calcium (Ca(2+)) chelator. Forskolin, an adenyl cyclase activator, conferred a similar effect. Iloprost and treprostinil increased intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels, and iloprost also increased intracellular Ca(2+). Iloprost suppressed poly I:C-induced mitogen-activated protein kinase (MAPK) phospho-p38 and phospho-activating transcription factor (ATF)2 expression. Iloprost downregulated poly I:C-induced histone H3K4 trimethylation in the TNFA gene promoter region via suppressing translocation of histone 3 lysine 4 (H3K4)-specific methyltransferases MLL (mixed lineage leukemia) and WDR5 (WD repeat domain 5). Iloprost-treated mDCs inhibited IL-13, IFN-γ and IL-10 production by T cells. In conclusion, PGI(2) analogs enhance IL-10 and suppress TNF-α expression through the IP/EP2/EP4 receptors-cAMP and EP1 receptor-Ca(2+) pathway. Iloprost suppressed TNF-α expression via the MAPK-p38-ATF2 pathway and epigenetic regulation by downregulation of histone H3K4 trimethylation.

Highlights

Asthma is a chronic airway inflammatory disorder with accumulation of inflammatory cells including eosinophils, lymphocytes, neutrophils and mast cells
To investigate the potential effect of Prostaglandin I2 (PGI2) analogs on the expression of cytokines in human myeloid dendritic cells (mDCs), mDCs isolated from healthy subjects were treated with varying doses of iloprost or treprostinil, either alone or in combination with tolllike receptor (TLR)-3 agonist polycytidylic acid (poly I):C
PGI2 analogs are peroxisome proliferator–activated receptors (PPARs) ligands with antiinflammatory actions [25] and our previous work demonstrated that iloprost and treprostinil modulate chemokines expression partly via PPARs in human monocytes [20], the present study revealed that the PPARs were not involved in the modulatory effect of PGI2 analogs on IL-10 and Tumor necrosis factor (TNF)-α expression in human mDCs

Summary

Introduction

Asthma is a chronic airway inflammatory disorder with accumulation of inflammatory cells including eosinophils, lymphocytes, neutrophils and mast cells. Tumor necrosis factor (TNF)-α, a pleiotropic proinflammatory cytokine, is increased in TNF-α mRNA and protein levels in the airways of asthmatic patients [2]. Emerging evidence suggests the central role of TNF-α in asthma for its properties of developing mast cell–mediated airway hyperresponsiveness, activating eosinophil proliferation and regulating chemokine production in monocytes [3]. EFFECT OF PGI2 ANALOGS ON HUMAN MYELOID DCS of TNF-α in severe refractory asthma according to its properties of neutrophil recruitment, induction of resistance to steroid and involvement of airway remodeling [4]. In contrast to TNF-α, the level of IL-10 in the lungs of asthmatic patients is significantly decreased [8]

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Discussion

Conclusion