Induction of cytochromes P-450 1A1 and 1B1 by motorcycle exhaust particulate in human breast cancer MCF-7 cells

The use of a 0.20 μm particulate matter filter decreases cytotoxicity in lung epithelial cells following air-liquid interface exposure to motorcycle exhaust

This study was designed to investigate whether the use of a 0.20 μm particulate matter (PM) filter reduced the cytotoxicity induced by motorcycle exhaust (ME), a mixture of gases and particles, in lung epithelial cells cultured in air-liquid interface (ALI) inserts. The concentrations of PM, carbon monoxide, carbon dioxide, total hydrocarbons (THC), total volatile organic compounds, and nitrogen oxides in both filtered ME (fME) by a 0.20 μm filter and non-filtered ME (non-fME) were measured. Lung epithelial cells were exposed to clean air, fME, or non-fME in the ALI chamber. Cell relative viabilities (CRV) and the reactive oxygen species (ROS) generation were determined. Our results revealed that PM_2.5 was the main compound of PM in ME. After filtration, PM and THC levels were significantly reduced, as compared with non-fME. When compared with the clean air exposed group, the CRV in both fME and non-fME-exposed group was significantly reduced (p < 0.001), while their ROS generation were markedly increased (p < 0.001). When compared with non-fME-exposed group, the CRV and ROS generation were significantly improved following fME exposure (p < 0.05). As a result, of PM and THC concentrations were decreased approximately 90% and 22.71%, respectively, the CRV was improved from 40.4% (non-fME) to 55.7% (fME), and the increased ROS generation by non-fME was decreased about 51.6%. When BEAS-2B cells were exposed to fME, a time-dependent reduction in CRV was observed. In conclusion, our findings suggest that ME-exposure in the ALI system induces cytotoxicity and oxidative stress responses. The addition of a 0.20 μm PM filter significantly modifies the particulate composition in PM and the concentration of THC, and shows protective effects by improving the survival of exposed lung epithelial cells and reducing the ROS generation. Therefore, emission factors such as different size of PM and THC from motorcycles may play a role in ME-induced toxicity.

Induction of fibroblast growth factor-9 and interleukin-1alpha gene expression by motorcycle exhaust particulate extracts and benzo(a)pyrene in human lung adenocarcinoma cells

Motorcycle exhaust particulates (MEP) contain carcinogenic polycyclic aromatic hydrocarbons including benzo(a)pyrene. This study has determined the ability of MEP to alter the expression of select genes from drug metabolism, cytokine, oncogene, tumor suppressor, and estrogen signaling families of human lung adenocarcinoma CL5 cells. cDNA microarray analyses and confirmation studies were performed using CL5 cells treated with 100 microg/ml MEP extract for 6 h. The results showed that MEP increased the mRNA levels of metabolic enzymes CYP1A1 and CYP1B1, proinflammatory cytokines interleukin (IL)-1alpha, IL-6, and IL-11, fibroblast growth factor (FGF)-6 and FGF-9, vascular endothelial growth factor (VEGF)-D, oncogene fra-1, and tumor suppressor p21. In contrast, MEP decreased tumor suppressor Rb mRNA in CL5 lung epithelial cells. Treatment with 10 microM benzo(a)pyrene for 6 h altered gene expression profiles, in a manner similar to those by MEP. Induction of IL-1alpha, IL-6, IL-11, and FGF-9 mRNA by MEP and benzo(a)pyrene was concentration and time dependent. Cotreatment with 2 mM N-acetylcysteine blocked the MEP- and benzo(a)pyrene-mediated induction. Treatment with MEP or benzo(a)pyrene increased IL-6 and IL-11 releases to CL5 cell medium. Incubation of human lung fibroblast WI-38 with MEP- or benzo(a)pyrene-induced CL5 conditioned medium for 4 days stimulated cell growth of the fibroblasts. Inhalation exposure of rats to 1:10 diluted motorcycle exhaust 2 h daily for 4 weeks increased CYP1A1, FGF-9, and IL-1alpha mRNA in lung. This present study shows that MEP and benzo(a)pyrene can induce metabolic enzyme, inflammatory cytokine, and growth factor gene expression in CL5 cells and stimulate lung epithelium-fibroblast interaction.

Induction of CYP1A1 and CYP1B1 and formation of carcinogen-DNA adducts in normal human mammary epithelial cells treated with benzo[a]pyrene

Inter-individual variation in formation of carcinogen-DNA adducts and induction of cytochrome P450 genes was measured in 23 cultured normal human mammary epithelial cell (NHMEC) strains established from reduction mammoplasty tissue. Semi-confluent cells were exposed to 4 microM benzo[a]pyrene (BP) for 12 h and BP-DNA adduct levels were measured by chemiluminescence immunoassay using antiserum elicited against DNA modified with r7, t8-dihydroxy-t-9, 10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE). BP-DNA adduct levels for 22 of 23 different cell strains ranged from non-detectable (three samples) to about 15 adducts/10(8) nucleotides. Increases in levels of CYP1A1 and CYP1B1 were detected using both oligonucleotide arrays and reverse transcription/quantitative real-time polymerase chain reactions (RT-PCRs). For CYP1A1 and CYP1B1, the oligonucleotide array data and RT-PCR data were highly correlated (r=0.73 and 0.70, respectively), suggesting that oligonucleotide arrays are a suitable gene discovery tool, and demonstrating that the complementary and efficient RT-PCR may be used to confirm microarray data for a specific gene in a large number of samples. As measured by RT-PCR, inter-individual variation in CYP1A1 induction was 100-fold, while the variation in CYP1B1 induction was almost 40-fold. On a per-person basis, CYP1A1 and CYP1B1 induction were well-correlated (r=0.88, P<0.001), which is to be expected as they are under the control of a common transcriptional regulation mechanism in response to BP exposure. Inter-individual variation in carcinogen-DNA adduct formation could not be explained only by variation in levels of CYP1A1 or CYP1B1 induction, as neither was well-correlated with BPDE-DNA adduct level (r=0.40 and 0.50 for CYP1A1 and CYP1B1, respectively). Evaluation of glutathione-S-transferase M1 genotype (GSTM1 positive or null) revealed an apparent correlation between positive GSTM1 genotype and BPDE-DNA adduct levels (r=0.84 and 0.77 for CYP1A1 and CYP1B1, respectively); however, after removal of the single outlier this relationship was not significant. Overall the data suggest that BPDE-DNA adduct levels in normal human breast tissue may be modulated by multiple factors that include, but are not exclusive to, CYP1A1 and CYP1B1 inducibility and the presence or absence of GSTM1.

Effects of amitraz on cytochrome P450-dependent monooxygenases and estrogenic activity in MCF-7 human breast cancer cells and immature female rats

This study investigated the ability of amitraz, a formamidine insecticide, to induce cytochrome P450-dependent monooxygenases and to disrupt estrogenic activity in human breast cancer MCF-7 cells and immature female rats. In MCF-7 cells, treatment with 10 microM amitraz for 24 h increased 7-ethoxyresorufin O-deethylase activity in cell homogenate. Treatment of MCF-7 cells with 1 and 10 microM amitraz for 3 h replaced previously bound [(3)H]17beta-estradiol (E(2)) from estrogen receptors. Treatment with 0.1 and 1 microM amitraz for 2 days inhibited [(3)H]thymidine incorporation into the DNA of MCF-7 cells while the inhibition was blocked in cells co-treated with 1 nM E(2) and amitraz. In immature female rats, treatment with 50 mg/kg amitraz intraperitoneally for 3 days increased cytochrome P450 content, 7-ethoxyresorufin, methoxyresorufin and pentoxyresorufin O-dealkylases, and benzo[a]pyrene hydroxylase activities in liver microsomes. The results of immunoblot analysis revealed that amitraz induced liver microsomal CYP1A1/2, 2B1/2B2, and 3A proteins. Treatment with 10 and 25 mg/kg amitraz for 3 days dose-dependently decreased uterine weight and peroxidase activity in immature female rats while the decreases were blocked in rats co-treated with 10 microg/kg E(2) and 10 or 25 mg/kg amitraz. These in vitro and in vivo findings suggest that amitraz induces multiple forms of P450 and exerts weak antiestrogenic activity.

Effects of motorcycle exhaust inhalation exposure on cytochrome P-450 2B1, antioxidant enzymes, and lipid peroxidation in rat liver and lung

The effects of motorcycle exhaust (ME) on metabolic and antioxidant enzymes and lipid peroxidation were determined using male rats exposed to 1:10 diluted ME by inhalation 2 h daily for 4 wk. For microsomal cytochrome P-450 enzymes, ME resulted in threefold increases of 7-ethoxyresorufin and pentoxyresorufin O-deethylase activities in liver and a sixfold increase of 7-ethoxyresorufin O-deethylase activity and an 80% decrease of pentoxyresorufin O-dealkylase activity in lung. The results of immunoblot analysis of microsomal proteins revealed that ME increased liver and lung cytochrome P-450 1A1 with minimal effects on cytochrome P-450 2E1. ME increased cytochrome P-450 2B1/2 proteins in liver but decreased cytochrome P-450 2B1 in lung. ME did not change microsomal cytochrome P-450 enzyme activity or protein level in kidney. For phase II enzymes, ME resulted in 53% and twofold increases of cytosolic NAD(P)H:quinone oxidoreductase activities in liver and lung, respectively, and no effect on microsomal UDP-glucuronosyltransferase activities. For antioxidant enzymes, ME produced 23% and 35% decreases of superoxide dismutase, 9% and 27% decreases of catalase, and no changes of glutathione peroxidase activities in liver and lung cytosols, respectively. For lipid peroxidation, the results of thiobarbituric acid assay showed that ME resulted in a twofold increase of formation of malondialdehyde by liver microsomes incubated with FeCl(3) -ADP. ME produced a threefold increase of malondialdehyde formation by lung microsomes. The present study demonstrates that ME inhalation exposure differentially modulates cytochrome P-450 2B1 and antioxidant enzymes and increases susceptibility to lipid peroxidation in rat liver and lung.