title: Prolactin induces MFG-E8 production in macrophages via transcription factor C/EBPbeta-dependent pathway.
abstract: The lactogenic hormone prolactin (PRL) regulates milk protein gene expression in mammary glands. To maintain homeostatic balance in the body, milk fat globule epidermal growth factor 8 (MFG-E8) is vital for phagocytic clearance of apoptotic cells. We investigated the effects of PRL on MFG-E8 expression in macrophages by evaluating its promoter function. Macrophages were stimulated with PRL, and the expression of MFG-E8 was determined using real-time PCR and Western blotting. The role of MFG-E8 on phagocytosis of apoptotic cells in PRL-treated macrophages was assessed using microscopy, while the response of PRL to MFG-E8 expression was evaluated using luciferase assay. Following treatment with PRL, significant up-regulations of the PRL receptor and MFG-E8 were observed in macrophages, though PRL-treated macrophages more efficiently engulfed apoptotic cells. The results of MFG-E8 promoter analysis showed considerable up-regulation of promoter activity in macrophages following PRL treatment and results from mutation analysis of the MFG-E8 promoter suggested that the C/EBPbeta binding site was responsible for PRL-induced activation of the MFG-E8 promoter. C/EBPbeta activity was found to be up-regulated in PRL-treated cells as revealed by an electrophoretic mobility shift assay (EMSA). In conclusion, PRL is a potent inducer of MFG-E8 expression in macrophages, while its effect is mediated by the presence of a responsive element in the MFG-E8 promoter.
authors.affiliation: Department of Internal Medicine II, Shimane University School of Medicine, 89-1, Enya-cho, Izumo, Shimane, Japan.
authors.forename: Md Monowar
authors.initials: MM
authors.lastname: Aziz
authors.forename: Shunji
authors.initials: S
authors.lastname: Ishihara
authors.forename: Mohammad Azharul Karim
authors.initials: MA
authors.lastname: Rumi
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Mishima
authors.forename: Naoki
authors.initials: N
authors.lastname: Oshima
authors.forename: Chikara
authors.initials: C
authors.lastname: Kadota
authors.forename: Ichiro
authors.initials: I
authors.lastname: Moriyama
authors.forename: Yong-Yu
authors.initials: YY
authors.lastname: Li
authors.forename: Farzana Binte
authors.initials: FB
authors.lastname: Rahman
authors.forename: Aya
authors.initials: A
authors.lastname: Otani
authors.forename: Akihiko
authors.initials: A
authors.lastname: Oka
authors.forename: Norihisa
authors.initials: N
authors.lastname: Ishimura
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Kadowaki
authors.forename: Yuji
authors.initials: Y
authors.lastname: Amano
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Kinoshita
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000096:biosynthesis* / Q000235:genetics; D017209:Apoptosis / Q000502:physiology*; D001483:Base Sequence; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000502:physiology*; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D017737:Macrophages, Peritoneal / Q000187:drug effects* / Q000502:physiology*; D051379:Mice; D008894:Milk Proteins / Q000096:biosynthesis* / Q000235:genetics; D010587:Phagocytosis / Q000187:drug effects; D011388:Prolactin / Q000494:pharmacology*; D011401:Promoter Regions, Genetic; D021381:Protein Transport; D011981:Receptors, Prolactin / Q000096:biosynthesis; D015854:Up-Regulation
chemical_list: D000954:Antigens, Surface; D022782:CCAAT-Enhancer-Binding Protein-beta; C490919:Mfge8 protein, mouse; D008894:Milk Proteins; D011981:Receptors, Prolactin; D011388:Prolactin