The Role of NF-κB as a Survival Factor in Environmental Chemical-Induced Pre-B Cell Apoptosis
- 1Boston University Schools of Public Health and Medicine, Department of Environmental Health (K.K.M., J.J.S., D.H.S., S.Q.) and 2Boston University School of Medicine, Department of Microbiology (S.D.), Boston, Massachusetts
Abstract
Polycyclic aromatic hydrocarbons (PAH) are ubiquitous environmental chemicals that suppress the immune system at multiple levels, including at the level of B cell development in the bone marrow microenvironment. Specifically, PAH induce preB cell apoptosis in primary bone marrow cultures and in cocultures of an early preB cell line (BU-11) and a bone marrow stromal cell line (BMS2). Previous studies focused on the molecular mechanisms through which PAH induce stromal cells to deliver an apoptosis signal to adjacent preB cells. Apoptosis signaling within the preB cell itself was not investigated. Here, the role of NF-κB, a lymphocyte survival factor, in PAH-induced preB cell apoptosis was assessed. Analysis of DNA-binding proteins extracted from the nuclei of untreated BU-11 cells indicated DNA-binding complexes comprising NF-κB subunits p50, c-Rel, and/or Rel A. NF-κB down-regulation with previously described inhibitors induced BU-11 cell apoptosis, demonstrating that the default apoptosis pathway blocked by NF-κB is functional at this early stage in B cell development. Similarly, exposure of BU-11/BMS2 cocultures to 7,12-dimethylbenz[a]anthracene (DMBA), a prototypic PAH, down-regulated nuclear Rel A and c-Rel before overt apoptosis. Finally, ectopic expression of Rel A or c-Rel rescued BU-11 cells from DMBA-induced apoptosis. These results extend previous observations by demonstrating that 1) NF-κB is a survival factor at an earlier stage of B cell development than previously appreciated and 2) NF-κB down-regulation is likely to be part of the molecular mechanism resulting in PAH-induced preB cell apoptosis. These results suggest nonclonally restricted, PAH-mediated suppression of B lymphopoiesis.
Footnotes
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Send reprint requests to: David H. Sherr, Ph.D., Boston University School of Public Health, 801 Albany St. Rm S105, Boston, MA 02118. E-mail: dsherr{at}bu.edu
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Supported by National Institutes of Health Grant RO1-ES06086, Superfund Basic Research Grant #1P42ES 07381, an EPA STAR fellowship to K.K.M., and an NRSA fellowship to J.J.S.
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D.H.S. and S.Q. contributed equally to this project.
- Abbreviations:
- PAH
- polycyclic aromatic hydrocarbon(s)
- DMBA
- 7,12-dimethylbenz[a]anthracene
- EMSA
- electromobility gel shift assay(s)
- NF-κB
- nuclear factor κB
- IκB
- inhibitor κB
- MG-132
- Z-Leu-Leu-Leu-CHO
- PDTC
- pyrrolidinedithiocarbamate
- PI
- propidium iodide
- sIg
- surface Ig
- TPCK
- N-tosyl-l-phenylalanine chloromethyl ketone
- PBS
- phosphate-buffered saline
- BrdU
- bromodeoxyuridine
- PAGE
- polyacrylamide gel electrophoresis
- IL
- interleukin
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- Received May 8, 2000.
- Accepted November 8, 2000.
- The American Society for Pharmacology and Experimental Therapeutics
