Abstract
NAD(P)H:quinone oxidoreductase 1 (NQO1) deficiency resulting from a homozygous NQO1*2 polymorphism has been associated with an increased risk of benzene-induced myeloid toxicity and a variety of de novo and therapy-induced leukemias. Endothelial cells in human bone marrow form one of the two known hematopoietic stem cell microenvironments and are one of the major cell types that express NQO1 in bone marrow. We have used a transformed human bone marrow endothelial cell (TrHBMEC) line to study the potential impact of a lack of NQO1 activity on adhesion molecule [endothelial leukocyte adhesion molecule 1 (E-selectin), vascular cell adhesion molecule (VCAM)-1, and intercellular adhesion molecule (ICAM)-1] expression and functional adhesion to bone marrow progenitor cells. We used both 5-methoxy-1,2-dimethyl-3-[(4-nitrophenoxy)methyl]indole-4,7-dione (ES936), a mechanism-based inhibitor of NQO1, and anti-NQO1 small interfering RNA to abrogate NQO1 activity. Real-time reverse transcription-polymerase chain reaction data demonstrated a significant inhibition of tumor necrosis factor (TNF)α-induced E-selectin mRNA levels after ES936 pretreatment. Immunoblot assays demonstrated a significant reduction in TNFα-stimulated E-selectin, VCAM-1, and ICAM-1 proteins after inhibition or knockdown of NQO1. The mechanisms underlying this effect remain undefined, but modulation of nuclear factor-κB (p65), c-Jun, and activating transcription factor 2, transcriptional regulators of adhesion molecules, were observed after inhibition or knockdown of NQO1. Decreased level of E-selectin, VCAM-1, and ICAM-1 also resulted in a functional deficit in adhesion. A parallel plate flow chamber study demonstrated a marked reduction in CD34+ cell (KG1a) adhesion to NQO1-deficient TrHBMECs relative to controls. The reduced adhesive ability of TrHBMECs may affect the function of the vascular stem cell niche and also may contribute to the increased susceptibility of polymorphic individuals lacking NQO1 to leukemias and hematotoxicants such as benzene.
Footnotes
This work was supported by National Institutes of Health National Institute of Environmental Health Sciences [Grant ES09554].
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
doi:10.1124/jpet.110.167841.
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ABBREVIATIONS:
- NQO1
- NAD(P)H:quinone oxidoreductase 1
- E-selectin
- endothelial leukocyte adhesion molecule 1
- HPC
- hematopoietic progenitor cell
- TrHBMEC
- transformed human bone marrow endothelial cell
- TNF
- tumor necrosis factor
- ES936
- 5-methoxy-1,2-dimethyl-3-[(4-nitrophenoxy)methyl]indole-4,7-dione
- VCAM
- vascular cell adhesion molecule
- ICAM
- intercellular cell adhesion molecule
- siRNA
- small interfering RNA
- IκB
- inhibitor of nuclear factor-κB
- PARP
- poly(ADP-ribose) polymerase
- RT-PCR
- reverse transcription-polymerase chain reaction
- DMSO
- dimethyl sulfoxide
- NF-κB
- nuclear factor-κB
- ATF
- activating transcription factor
- HSC
- hematopoietic stem cell
- JNK
- c-Jun NH2-terminal kinase.
- Received March 2, 2010.
- Accepted April 5, 2010.
- Copyright © 2010 by The American Society for Pharmacology and Experimental Therapeutics