Prolactin induces MFG-E8 production in macrophages via transcription factor C/EBPbeta-dependent pathway.
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.
Aziz
Md Monowar
MM
Department of Internal Medicine II, Shimane University School of Medicine, 89-1, Enya-cho, Izumo, Shimane, Japan.
Ishihara
Shunji
S
Rumi
Mohammad Azharul Karim
MA
Mishima
Yoshiyuki
Y
Oshima
Naoki
N
Kadota
Chikara
C
Moriyama
Ichiro
I
Li
Yong-Yu
YY
Rahman
Farzana Binte
FB
Otani
Aya
A
Oka
Akihiko
A
Ishimura
Norihisa
N
Kadowaki
Yasunori
Y
Amano
Yuji
Y
Kinoshita
Yoshikazu
Y
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
D000954:Antigens, Surface; D022782:CCAAT-Enhancer-Binding Protein-beta; C490919:Mfge8 protein, mouse; D008894:Milk Proteins; D011981:Receptors, Prolactin; D011388:Prolactin