DEPLETION OF GLUTATHIONE BY BENZO(A)PYRENE METABOLITES, IONOMYCIN, THAPSIGARGIN, AND PHORBOL-MYRISTATE IN HUMAN PERIPHERAL-BLOOD MONONUCLEAR-CELLS

Previous studies in this laboratory have shown that polycyclic aromati c hydrocarbons (PAHs) alter Ca2+ homeostasis and inhibit activation of both B and T lymphocytes obtained from rodents and humans. Tn the pre sent studies, we demonstrate that cr-naphthoflavone (ANF), an inhibito r of cytochrome P4501A activity, reduced the Ca2+ elevation produced b y BaP in human peripheral blood mononuclear cell (HPBMC) lymphocytes. These results suggested that BaP metabolites may play a role in intrac ellular Ca2+ homeostasis in human lymphocytes. Reactive oxidative inte rmediates of BaP produced in HPMBC are known to be highly carcinogenic and have also been shown to be immunosuppressive. We examined the eff ects of benzo(a)pyrene (BaP), 7,12-dimethylbenz(a)anthracene (DMBA), b enzo(e)pyrene (BeP), and anthracene, as well as certain BaP metabolite s, on the levels of intracellular Ca2+ and glutathione in HPBMC. While BaP, DMBA, BeP, and anthracene did not cause a statistically signific ant decrease in GSH in HPBMC at concentrations of 1 or 10 mu M followi ng a 6-, 48-, or 72-hr exposure, reactive BaP metabolites including 4, 5-epoxide BaP and 7,8-diol-9,10-epoxide BaP consistently produced a 20 -30% depletion of glutathione in HPBMC following a 6-hr treatment peri od. These BaP metabolites also elevated intracellular Ca2+ in HPBMC du ring a 6-hr incubation. Results of these experiments suggest that meta bolism of BaP to certain epoxide metabolites may be responsible for su lfhydryl damage leading to transient GSH depletion and Ca2+ elevation. These results are consistent with the hypothesis that sulfhydryl dama ge by certain PAH metabolites may lead to altered Ca2+ homeostasis, le ading to inhibition of cell activation and proliferation in HPBMC. (C) 1997 Academic Press.