Background Benzo(a)pyrene (BaP), anthracene (ANTH) and chrysene (CHRY) are polynuclear aromatic hydrocarbons (PAHs) implicated in renal toxicity and carcinogenesis. M) for 24 hr. Total RNA and protein will be harvested for Northern analysis and measurements of aryl hydrocarbon hydroxylase (AHH) and ethoxyresorufin-O-deethylase (EROD) activity, respectively, to evaluate cytochrome P450 mRNA and protein 6823-69-4 manufacture inducibility. Cellular hydrocarbon uptake and metabolic profiles of PAHs were analyzed by high performance liquid chromatography (HPLC). Results Combined hydrocarbon treatments did not influence the cellular uptake of individual hydrocarbons. ANTH or CHRY strongly repressed BaP-inducible cytochrome P450 mRNA and protein manifestation, and markedly inhibited oxidative BaP rate of metabolism. Conclusion These findings show that antagonistic relationships among nephrocarcinogenic PAHs involve modified 6823-69-4 manufacture manifestation of cytochrome P450s that modulate bioactivation profiles and nephrotoxic/ nephrocarcinogenic potential. Background The biological effects of PAHs are often mediated by oxidative rate of metabolism of the parent hydrocarbon to reactive intermediates that adduct DNA and induce oxidative stress . In the kidney, PAHs elicit cell type-specific effects that differentially influence glomerular versus tubular epithelial cell Rabbit Polyclonal to ANKRD1 structure and function. BaP and ANTH selectively injure glomerular mesangial cells, while CHRY preferentially focuses on cortico-tubular epithelial cells [2,3]. The study of single chemical 6823-69-4 manufacture effects has offered fundamental information within the nephrotoxic potential of specific PAHs, but human being exposure to these group of chemicals is definitely hardly ever limited to a 6823-69-4 manufacture single agent, and most often entails exposure to PAH mixtures . Thus, a more practical approach is to evaluate the cellular, biochemical, and molecular mechanisms by which PAHs interact to produce additive, synergistic or antagonistic interactions. Such studies possess shown that binary and ternary mixtures of PAHs yield paradoxical antagonistic relationships in vitro . A toxicological connection is a circumstance in which exposure to 6823-69-4 manufacture two or more chemicals results in qualitative or quantitative modulation of the biological response elicited by individual agents. Toxicological interactions may be mediated by changes in the absorption, distribution, metabolism and excretion of one or more of the chemicals present in the mixture. Since the ability of PAHs to compromise cellular and genomic integrity often requires bioactivation by cytochrome P-450 enzymes (CYPs) to reactive intermediates, their role in PAH-induced environmental diseases is profound . The conversation of PAHs with CYPs is usually unique in that the expression of genes that encode for CYP-associated activities is usually itself regulated by the PAH substrates they metabolize. Shimada et al.  have shown that BaP and CHRY induce Cyp1a1 and 1b1 through the aryl hydrocarbon receptor (Ahr), and that the enzymes encoded by these genes mediate toxicity and tumorigenicity. The Ahr belongs to the basic helix loop helix/PAS family of proteins . The activation of cytoplasmic complexes made up of the Ahr depends on ligand binding to the receptor, nuclear translocation and formation of active heterodimers with a nuclear protein called Arnt . The AhR-Arnt complex binds to s pecific cis-acting responsive elements known as xenobiotic responsive elements located in the promoters and enhancers of target genes, including CYPs themselves . PAHs or halogenated aromatic hydrocarbons function as ligands of the Ahr. The present studies were conducted to evaluate profiles of Cyp1a1 and Cyp1b1 inducibility in binary PAH mixtures, and their impact on BaP bioactivation. Evidence is presented that chemical-specific differences in the regulation of Cyp1a1 and Cyp1b1 contribute to differential metabolic activation of PAHs in binary mixture. On the basis of these findings it is concluded that interactions between BaP, ANTH and CHRY involve altered expression of cytochrome P450s that modulate bioactivation profiles and nephrotoxic/ nephrocarcinogenic potential. Materials and Methods Materials BaP, ANTH and CHRY were purchased from Sigma Chemical Co. (St. Louis, MO). RPMI 1640 and M199 were purchased from GIBCO-BRL (Grand Island, NY, USA). All other chemicals were from Sigma Chemical Co. Cell culture/chemical treatments Rat glomerular mesangial cells in serial culture were seeded on 6-well plates at a density of 200 cells/mm2. At least three replicates were used for each chemical concentration tested in multiple experiments. The concentrations examined are similar to those used in previous studies and representative of those encountered in the environment. Cultures were challenged with selected PAHs for 24 hr at concentrations.