title: Activation of the aryl hydrocarbon receptor/transcription factor and bone marrow stromal cell-dependent preB cell apoptosis.
abstract: In the absence of known endogenous ligands, investigators have exploited ubiquitous environmental pollutants, including polycyclic aromatic hydrocarbons, to gain insight into the physiologic functions of the aryl hydrocarbon (dioxin) receptor/transcription factor (AhR). AhR ligands induce cell transformation and steroid-like immunosuppression, suggesting a role for the AhR in regulation of cell growth and/or function. However, mechanisms through which the AhR influences cells in general and lymphocytes in particular remain unresolved. A murine model of B cell development was created to: 1) examine a role for the AhR in immunosuppression; 2) define mechanisms of AhR ligand immunosuppression; 3) characterize AhR expression in preB cells, in bone marrow stromal cells that support preB cells, or in primary bone marrow B cells; and 4) determine if AhR ligands suppress lymphopoiesis by acting directly on preB cells or indirectly via the microenvironment, as represented by bone marrow stromal cells. Results indicate that: 1) low doses (> or = 10(-8) M) of the prototypic AhR ligand, 7,12-dimethylbenz[a]anthracene (DMBA), induce preB cell apoptosis in 12 to 24 h; 2) alpha-naphthoflavone, an AhR and cytochrome P-450 inhibitor, blocks DMBA-induced apoptosis; 3) AhR mRNA and functional AhR protein are expressed at high levels in bone marrow stromal cells (little or no AhR is present in preB cell lines), and 4) preB cells maintained in rIL-7 do not undergo DMBA-induced apoptosis unless cultured with stromal cells. Results underscore the regulatory role played by bone marrow stromal cells in lymphopoiesis and support the hypothesis that the AhR effects immunosuppression by inducing stromal cells to deliver a death signal to lymphocytes.
authors.affiliation: Department of Environmental Health, Boston University Schools of Medicine and Public Health, MA 02118, USA.
authors.forename: K
authors.initials: K
authors.lastname: Yamaguchi
authors.forename: R I
authors.initials: RI
authors.lastname: Near
authors.forename: R A
authors.initials: RA
authors.lastname: Matulka
authors.forename: A
authors.initials: A
authors.lastname: Shneider
authors.forename: P
authors.initials: P
authors.lastname: Toselli
authors.forename: A F
authors.initials: AF
authors.lastname: Trombino
authors.forename: D H
authors.initials: DH
authors.lastname: Sherr
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001402:B-Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D001571:Benzoflavones / Q000494:pharmacology; D001667:Binding, Competitive; D001853:Bone Marrow / Q000378:metabolism*; D001854:Bone Marrow Cells; D002460:Cell Line; D065607:Cytochrome P-450 Enzyme Inhibitors; D006412:Hematopoietic Stem Cells / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D012333:RNA, Messenger / Q000096:biosynthesis; D018336:Receptors, Aryl Hydrocarbon / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D017154:Stromal Cells / Q000378:metabolism; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
chemical_list: D001571:Benzoflavones; D065607:Cytochrome P-450 Enzyme Inhibitors; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; D014157:Transcription Factors; D015127:9,10-Dimethyl-1,2-benzanthracene; C011512:alpha-naphthoflavone