title: Epigenetic synergism between interleukin-4 and aryl-hydrocarbon receptor in human macrophages.
abstract: The aryl hydrocarbon receptor (AhR)-ligand axis is involved in immune regulation, but its molecular basis remains to be fully elucidated. Chemokine (C-C motif) ligand 1 (CCL1) is an important chemoattractant, but how CCL1 is regulated remains to be defined. The role of AhR in regulating CCL1 expression in two major subsets of macrophage was investigated. We used a human THP-1 cell line, monocytes, and mouse peritoneal macrophages to generate M(IFN-γ/LPS) and M(IL-4) subsets, and the AhR's ligand effect was determined by the use of a combination of chromatin immunoprecipitation, PCR, and ELISA. Upon exposure to a classical AhR ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), selective induction of CCL1 was noted only in M(IL-4), not M(IFN-γ/LPS) cells in human but not murine macrophages. This selectivity was mediated by AhR's binding to the distal dioxin-responsive element (DRE) in the CCL1 promoter of the M(IL-4) subset, and a deletion mutant lacking the distal DRE sequence lost its activity. In contrast to the M(IFN-γ/LPS) cells, the distal DRE was devoid of tri-methylated histone 3 lysine 27 (H3K27) in M(IL-4) cells, and the addition of a H3K27 demethylase inhibitor blocked AhR-mediated CCL1 expression. Similar selectivity of CCL1 expression was also noted in monocyte-derived M(IL-4) subsets, and the level of AhR binding to distal DRE in monocytes was correlated with the levels of plasma interleukin-4 (IL-4) in 23 human subjects. These findings suggested the existence of a new regulatory epigenetic-based mechanism, wherein AhR in concert with IL-4 differentially regulated human, not murine, macrophage CCL1 response.
  
  
  
  Human CCL1 gene is selectively targeted by AhR in M(IL-4) macrophage. IL-4-induced epigenetic modification potentiates AhR-mediated CCL1 expression. This epigenetic control of CCL1 expression is not operative in murine macrophages.
authors.affiliation: Department of Biotechnology, College of Life Science, Kaohsiung Medical University, Kaohsiung, 80708, Taiwan.|Department of Biological Sciences, National Sun Yat-Sen University, Kaohsiung, 80424, Taiwan.
authors.forename: Wei-Ting
authors.initials: WT
authors.lastname: Liao
authors.affiliation: Graduate Institute of Medical Science, Kaohsiung Medical University, Kaohsiung, 80708, Taiwan.
authors.forename: Jian-He
authors.initials: JH
authors.lastname: Lu
authors.affiliation: Department of Biotechnology, College of Life Science, Kaohsiung Medical University, Kaohsiung, 80708, Taiwan.
authors.forename: Wei-Ting
authors.initials: WT
authors.lastname: Wang
authors.affiliation: Department of Pediatrics, Kaohsiung Medical University Hospital and College of Medicine, Kaohsiung Medical University, Kaohsiung, 80708, Taiwan.|Department of Pediatrics, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung Medical University, Kaohsiung, 80145, Taiwan.
authors.forename: Chih-Hsing
authors.initials: CH
authors.lastname: Hung
authors.affiliation: Divison of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung, 80708, Taiwan.|Department of Internal Medicine, School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, 80708, Taiwan.
authors.forename: Chau-Chyun
authors.initials: CC
authors.lastname: Sheu
authors.affiliation: National Institute of Environmental Health Sciences, National Health Research Institutes, 35 Keyan Rd, Zhunan, Miaoli County, 35053, Taiwan. skhuang@nhri.org.tw.|Research Center for Environmental Medicine, Kaohsiung Medical University, Kaohsiung, 80708, Taiwan. skhuang@nhri.org.tw.|Johns Hopkins Asthma and Allergy Center, School of Medicine, Johns Hopkins University, Baltimore, MD, 21224, USA. skhuang@nhri.org.tw.
authors.forename: Shau-Ku
authors.initials: SK
authors.lastname: Huang
mesh_terms: D000818:Animals; D002460:Cell Line; D016764:Cell Polarity; D054402:Chemokine CCL1 / Q000235:genetics*; D065633:Cytochrome P-450 CYP1B1 / Q000235:genetics; D044127:Epigenesis, Genetic; D006801:Humans; D015847:Interleukin-4 / Q000235:genetics*; D008264:Macrophages / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics*
chemical_list: C065971:CCL1 protein, human; D054402:Chemokine CCL1; C508598:IL4 protein, human; D018336:Receptors, Aryl Hydrocarbon; D015847:Interleukin-4; C585496:CYP1B1 protein, human; D065633:Cytochrome P-450 CYP1B1
keywords: Aryl hydrocarbon receptor; Chemokine C-C motif ligand 1; Dioxin; Macrophage polarization