NF-κB signaling is increased in HD3 cells following exposure to 1,4-benzoquinone: role of reactive oxygen species and p38-MAPK.

In utero exposure to benzene, a known environmental contaminant, is associated with increased risk of leukemia. We have previously shown that in utero benzene exposure can alter the redox-sensitive transcription factor NF-κB, and we hypothesize that this is through benzene-induced reactive oxygen species (ROS) production interfering with the signaling pathway involving NF-κB and p38-Mitogen Activated Protein Kinase (MAPK). As benzoquinone (BQ) is one of benzene's most toxic metabolites, the objectives of this study were to determine whether ROS and p38-MAPK-mediated BQ-induced increased NF-κB activity. HD3 chicken erythroblast cells were transfected with an NF-κB luciferase-linked reporter plasmid and exposed to BQ (25 μM) for 2-24 h. NF-κB activities were determined through luciferase assays; Western blotting was conducted to assess changes in protein levels in nontransfected cells; and the presence of ROS was determined via 2',7'-dichlorodihydrofluorescein diacetate (DCFDA) flow cytometric assays. Results demonstrated that NF-κB activity was significantly increased following exposure to BQ for 16 and 24 h and DCFDA assays and pretreatment with antioxidants indicated that BQ-mediated ROS production was responsible for this increase. Furthermore, decreased inhibitor of kappaB-alpha (IκB-α) expression suggests that nuclear factor-kappaB (NF-κB) translocates into the nucleus and that p38-MAPK activation through a ROS-dependent pathway mediates BQ-mediated increases in NF-κB activity. Future studies investigating the role of p38-MAPK in this pathway are warranted. Evaluating the effects of toxicant exposure on cell signaling pathways is vital for understanding mechanisms of xenobiotic-induced toxicity.