Studies performed over the last decade suggest that the immunotoxicity of benzene depends on its metabolism to thiol-reactive quinones. The long-term objective of the proposed research is to identify the molecular mechanisms underlying the immunosuppressive effects of the benzene metabolite, p-benzoquinone (p-BQ). We have demonstrated that p-BQ suppresses the production of the T cell growth factor, interleukin-2 (IL- 2), and inhibits the formation of macrophage/T cell aggregates (agglutination). At the molecular level, we noted that P-BQ inhibits the expression of the IL-2 gene and c-fos genes. We hypothesize that p-BQ inhibits a signal transduction pathway that regulates both the expression of these genes and the phosphorylation of LFA-1Beta (CD11a), which mediates agglutination of T cells via an interaction with ICAM-1 molecules on macrophages. We propose a series of experiments using human mononuclear cells and the Jurkat T cell line to address the following specific aims: (1) To assess the role of macrophages and peroxidases in the immunosuppressive effects of the benzene metabolites, phenol, hydroquinol (HQ), and p-BQ; (2) To measure the effects of benzene metabolites on the expression of genes encoding interleukins and other cytokines; (3) To measure the effects of benzene metabolites on the induction of transcription factors (NF-AT, NFkappaB, AP-1, and Oct-1) that regulate IL-2 gene expression; (4) To determine if the inhibition of agglutination by p-BQ is due to inhibition of LFA-1Beta phosphorylation and/or inhibition of ICAM-1 (CD54) expression; (5) To measure the effects of the benzene metabolites on the activity of two critical PMA-inducible protein kinases, protein kinase C and calmodulin- dependent protein kinase; and (6) To determine if the effects of P-BQ on c-fos expression correlate with inhibition of induction of one of its 5' transcription factors or a factor that binds to and stabilizes the c-fos MRNA transcript. These experiments will provide evidence for the molecular targets of benzene immunotoxicity.
