title: Bone marrow stromal-B cell interactions in polycyclic aromatic hydrocarbon-induced pro/pre-B cell apoptosis.
abstract: Environmental polycyclic aromatic hydrocarbons (PAH) and related halogenated hydrocarbons are immunotoxic in a variety of systems. In a model system of B lymphopoiesis, PAH exposure rapidly induces apoptosis in CD43- pre-B and CD43+ pro/pre-B cells. Apoptosis induction by 7,12-dimethylbenzo[a]anthracene (DMBA) is dependent upon AhR+ bone marrow stromal cells and likely involves DMBA metabolism within the stromal cell. However, it is not known if PAH-treated stromal cells release free metabolites or soluble factors that may directly induce B cell death or if the effector death signal is delivered by stromal cell-B cell contact. Here, we demonstrate that supernatants from DMBA-treated bone marrow stromal cells contain an activity capable of inducing apoptosis in pro/pre-B cells cocultured with stromal cells. This activity (1) is not produced when stromal cells are cotreated with DMBA and alpha-naphthoflavone (alpha-NF), an aryl hydrocarbon receptor (AhR) and cytochrome P-450 inhibitor, (2) is > or = 50 kDa, (3) is trypsin and heat sensitive, and (4) is dependent on AhR+ stromal cells, which in turn deliver the effector death signal to pro/pre-B cells. The results (1) argue against a role for a soluble, stromal cell-derived cytokine as the effector of PAH-induced pro/pre-B cell death, (2) exclude the possibility of a free metabolite acting directly on AhR- pro/pre-B cell targets, and (3) suggest the elaboration by stromal cells of a relatively stable, DMBA metabolite-protein complex capable of acting on other stromal cells at some distance. Collectively, these studies suggest that, while stromal cell products, e.g., metabolite-protein complexes, may affect the function of distant stromal cells, the effector death signal delivered by stromal cells to bone marrow B cells is mediated by cell-cell contact.
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001402:B-Lymphocytes / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D001571:Benzoflavones / Q000494:pharmacology; D001854:Bone Marrow Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D017077:Culture Media, Conditioned / Q000737:chemistry / Q000494:pharmacology; D004785:Environmental Pollutants / Q000378:metabolism / Q000494:pharmacology*; D006412:Hematopoietic Stem Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018336:Receptors, Aryl Hydrocarbon / Q000037:antagonists & inhibitors / Q000378:metabolism; D017154:Stromal Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology
chemical_list: D001571:Benzoflavones; D017077:Culture Media, Conditioned; D004785:Environmental Pollutants; D018336:Receptors, Aryl Hydrocarbon; D015127:9,10-Dimethyl-1,2-benzanthracene; C011512:alpha-naphthoflavone