title: Benzene metabolite hydroquinone up-regulates chondromodulin-I and inhibits tube formation in human bone marrow endothelial cells.
abstract: Bone marrow is a major target of benzene toxicity, and NAD-(P)H:quinone oxidoreductase (NQO1), an enzyme protective against benzene toxicity, is present in human bone marrow endothelial cells, which form the hematopoietic stem cell vascular niche. In this study, we have employed a transformed human bone marrow endothelial cell (TrHBMEC) line to study the adverse effects induced by the benzene metabolite hydroquinone. Hydroquinone inhibited TrHBMEC tube formation at concentrations that were not overtly toxic, as demonstrated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide or sulforhodamine B analysis. Hydroquinone was found to up-regulate chondromodulin-I (ChM-I), a protein that promotes chondrocyte growth and inhibits endothelial cell growth and tube formation. Recombinant human ChM-I protein inhibited tube formation in TrHBMECs, suggesting that up-regulation of ChM-I may explain the ability of hydroquinone to inhibit TrHB-MEC tube formation. To explore this possibility further, anti-ChM-I small interfering RNA (siRNA) was used to deplete ChM-I mRNA and protein. Pretreatment with anti-ChM-I siRNA markedly abrogated hydroquinone-induced inhibition of tube formation in TrHBMECs. Overexpression of the protective enzyme NQO1 in TrHBMECs inhibited the up-regulation of ChM-I and abrogated the inhibition of tube formation induced by hydroquinone. In summary, hydroquinone treatment up-regulated ChM-I and inhibited tube formation in TrHBMECs; NQO1 inhibited hydroquinone-induced up-regulation of ChM-I in TrHB-MECs and protected cells from hydroquinone-induced inhibition of tube formation. This study demonstrates that ChM-I up-regulation is one of the underlying mechanisms of inhibition of tube formation and provides a mechanism that may contribute to benzene-induced toxicity at the level of bone marrow endothelium.
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy and Cancer Center, University of Colorado Denver, 12700 East 19th Avenue, Aurora, CO 80045, USA.
authors.forename: Hongfei
authors.initials: H
authors.lastname: Zhou
authors.forename: Jadwiga K
authors.initials: JK
authors.lastname: Kepa
authors.forename: David
authors.initials: D
authors.lastname: Siegel
authors.forename: Shigenori
authors.initials: S
authors.lastname: Miura
authors.forename: Yuji
authors.initials: Y
authors.lastname: Hiraki
authors.forename: David
authors.initials: D
authors.lastname: Ross
mesh_terms: D001554:Benzene / Q000378:metabolism* / Q000633:toxicity; D001854:Bone Marrow Cells / Q000187:drug effects*; D002460:Cell Line; D003094:Collagen; D004338:Drug Combinations; D042783:Endothelial Cells / Q000187:drug effects*; D006801:Humans; D006873:Hydroquinones / Q000378:metabolism / Q000633:toxicity*; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis* / Q000235:genetics; D007797:Laminin; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000096:biosynthesis; D011509:Proteoglycans; D012333:RNA, Messenger / Q000096:biosynthesis; D034741:RNA, Small Interfering / Q000235:genetics; D015854:Up-Regulation
chemical_list: D004338:Drug Combinations; D006873:Hydroquinones; D036341:Intercellular Signaling Peptides and Proteins; D007797:Laminin; D008565:Membrane Proteins; D011509:Proteoglycans; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C059485:matrigel; C068675:CNMD protein, human; D003094:Collagen; D016660:NAD(P)H Dehydrogenase (Quinone); C447479:NQO1 protein, human; D001554:Benzene; C031927:hydroquinone