title: Toll-like receptor 4-mediated cAMP production up-regulates B-cell activating factor expression in Raw264.7 macrophages.
abstract: B-cell activating factor (BAFF) plays a role in the generation and the maintenance of mature B cells. Lipopolysaccharide (LPS) increased BAFF expression through the activation of toll-like receptor 4 (TLR4)-dependent signal transduction. Here, we investigated the mechanism of action on mouse BAFF (mBAFF) expression by cAMP production in Raw264.7 mouse macrophages. mBAFF expression was increased by the treatment with a cAMP analogue, dibutyryl-cAMP which is the activator of protein kinase A (PKA), cAMP effector protein. PKA activation was measured by the phosphorylation of cAMP-response element binding protein (CREB) on serine 133 (S133). cAMP production and CREB (S133) phosphorylation were augmented by LPS-stimulation. While mBAFF promoter activity was enhanced by the co-transfection with pS6-RSV-CREB, it was reduced by siRNA-CREB. PKA inhibitor, H-89, reduced CREB (S133) phosphorylation and mBAFF expression in control and LPS-stimulated macrophages. Another principal cAMP effector protein is cAMP-responsive guanine nucleotide exchange factor (Epac), a Rap GDP exchange factor. Epac was activated by the treatment with 8-(4-chloro-phenylthio)-2'-O-methyladenosine-3',5'-cyclic monophosphate (CPT), Epac activator, as judged by the measurement of Rap1 activation. Basal level of mBAFF expression was increased by CPT treatment. LPS-stimulated mBAFF expression was also slightly enhanced by co-treatment with CPT. In addition, dibutyryl-cAMP and CPT enhanced mBAFF expression in bone marrow-derived macrophages (BMDM). With these data, it suggests that the activation of PKA and cAMP/Epac1/Rap1 pathways could be required for basal mBAFF expression, as well as being up-regulated in the TLR4-induced mBAFF expression.
authors.affiliation: Department of Bioscience and Biotechnology, Sejong University, Seoul 143-747, Republic of Korea. eunyimoon@sejong.ac.kr
authors.forename: Eun-Yi
authors.initials: EY
authors.lastname: Moon
authors.forename: Yu-Sun
authors.initials: YS
authors.lastname: Lee
authors.forename: Wahn Soo
authors.initials: WS
authors.lastname: Choi
authors.forename: Mi-Hee
authors.initials: MH
authors.lastname: Lee
mesh_terms: D000818:Animals; D053264:B-Cell Activating Factor / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000378:metabolism; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000096:biosynthesis*; D007546:Isoquinolines / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D013449:Sulfonamides / Q000494:pharmacology; D051197:Toll-Like Receptor 4 / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D053264:B-Cell Activating Factor; D007546:Isoquinolines; D008070:Lipopolysaccharides; D013449:Sulfonamides; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D000242:Cyclic AMP; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide