The involvement of secondary signaling molecules in cytochrome P-450 1A1-mediated inducible nitric oxide synthase expression in benzo(a)pyrene-treated rat polymorphonuclear leukocytes

Benzo(a)pyrene induces cytochrome P-450 1A1 (CYP1A1) expression in rat polymorphonuclear leukocytes (PMNs) that upregulates expression of inducible nitric oxide synthase (iNOS). In the present study, the involvement of secondary signaling molecules in CYP1A1-mediated augmentation of iNOS expression in benzo(a)pyrene-treated rat PMNs was investigated. PMNs were isolated from the peripheral blood of controls and benzo(a)pyrene-treated rats. The expression and/or activity of CYP1A1, iNOS, tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and intracellular calcium ([Ca2+]i) concentrations were measured in control and benzo(a)pyrene-treated rat PMNs with and without alpha-naphthoflavone, aminoguanidine, genistein, pyrrolidine dithiocarbamate (PDTC), felodipine, or SB202190 pre-treatment. A significant elevation in CYP1A1 and [Ca2+]i was observed in benzo(a)pyrene-treated rat PMNs, which was significantly restored by alpha-naphthoflavone or genistein. Neither PDTC, SB202190, nor aminoguanidine altered the benzo(a)pyrene-mediated increase in [Ca2+]i. Although felodipine reduced the benzo(a)pyrene-mediated increase in [Ca2+]i, no significant change was observed in CYP1A1 expression and activity. Benzo(a)pyrene-augmented iNOS expression and activity in PMNs were significantly reverse by felodipine, genistein, or PDTC. Benzo(a)pyrene also induced TNF-α and IL-1β production in PMNs, which was significantly reversed by genistein. The results demonstrated the involvement of [Ca2+]i, tyrosine kinase, inflammatory cytokines, and NF-κB in CYP1A1-mediated iNOS expression in benzo(a)pyrene-treated rat PMNs.