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N -nitrosonornicotine (NNN) and N -nitrosoanabasine (NAB) are both tobacco-specific nitrosamines bearing two heterocyclic amino groups, NAB bearing an extra -CH 2 - group (conferring a hexa- rather than penta-membered cycle) but with significantly decreased carcinogenicity. However, their activating enzymes and related mutagenicity remain unclear. In this study, the chemical-CYP interaction was analyzed by molecular docking, thus the binding energies and conformations of NNN for human CYP2A6, 2A13, 2B6, 2E1 and 3A4 appeared appropriate as a substrate, so did NAB for human CYP1B1, 2A6, 2A13 and 2E1. The micronucleus test in human hepatoma (HepG2) cells with each compound (62.5–1000 μM) exposing for 48 h (two-cell cycle) was negative, however, pretreatment with bisphenol AF (0.1–100 nM, CYPs inducer) and ethanol (0.2% v:v, CYP2E1 inducer) potentiated micronucleus formation by both compounds, while CITCO (1 μM, CYP2B6 inducer) selectively potentiated that by NNN. In C3A cells (endogenous CYPs enhanced over HepG2) both compounds induced micronucleus, which was abolished by 1-aminobenzotriazole (60 μM, CYPs inhibitor) while unaffected by 8-methoxypsoralen (1 μM, CYP2A inhibitor). Consistently, NNN and NAB induced micronucleus in V79-derived recombinant cell lines expressing human CYP2B6/2E1 and CYP1B1/2E1, respectively, while negative in those expressing other CYPs. By immunofluorescent assay both compounds selectively induced centromere-free micronucleus in C3A cells. In PIG-A assays in HepG2 cells NNN and NAB were weakly positive and simply negative, respectively; however, in C3A cells both compounds significantly induced gene mutations, NNN being slight more potent. Conclusively, both NNN and NAB are mutagenic and clastogenic, depending on metabolic activation by partially different CYP enzymes. [Display omitted] • Two tobacco-specific nitrosamines induced genotoxic effect in mammalian cells. • Genotoxicity of NNN was activated by human CYP2B6/2E1, and NAB by CYP1B1/2E1. • Pretreating HepG2 cells with bisphenol AF potentiated the effects of NNN and NAB. • The mode of chromosome damage by NNN and NAB were consistently pure clastogenesis. [ABSTRACT FROM AUTHOR]

Bisphenol compounds (BPs) are ubiquitously existing pollutants. Recent evidence shows that they may be activated by human CYP1A1 for clastogenic effects; however, factors that influence/mediate CYP1A1-activated 4,4′-(hexafluoroisopropylidene)diphenol (BPAF) toxicity, particularly the aryl hydrocarbon receptor (AhR), sulfotransferase (SULT) 1A1 [known to conjugate 2,2-bis(4-hydroxyphenol)-propane (BPA)] and reactive oxygen species (ROS), remain unclear. In this study, a human hepatoma (HepG2) cell line was genetically engineered for the expression of human CYP1A1 and SULT1A1, producing HepG2-hCYP1A1 and HepG2-hSULT1A1, respectively. They were used in the micronucleus test and γ-H2AX analysis (Western blot) (indicating double-strand DNA breaks) with BPAF; the role of AhR in mediating BPAF toxicity was investigated by coexposure of AhR modulators in HepG2 and its derivative C3A (with no genetic modifications but enhanced CYP expression). The results indicated induction of micronuclei by BPAF (≥ 2.5 µM, for 2-cell cycle) in HepG2-hCYP1A1 and C3A, while inactive in HepG2 and HepG2-hSULT1A1; however, BPAF induced micronuclei in HepG2 pretreated with 3,3′,4,4′,5-pentachlorobiphenyl (PCB126, AhR activator), and BAY-218 (AhR inhibitor) blocked the effect of BPAF in C3A. In HepG2-hCYP1A1 BPAF selectively induced centromere-free micronuclei (immunofluorescent assay) and double-strand DNA breaks. In HepG2 cells receiving conditional medium from BPAF-HepG2-hCYP1A1 incubation micronuclei were formed, while negative in HepG2-hSULT1A1. Finally, the intracellular levels of ROS, superoxide dismutase and reduced glutathione in C3A and HepG2-hCYP1A1 exposed to BPAF were all moderately increased, while unchanged in HepG2 cells. In conclusion, like other BPs BPAF is activated by human CYP1A1 for potent clastogenicity, and this effect is enhanced by AhR while alleviated by SULT1A1. [Display omitted] • Bisphenol AF (BPAF) induces chromosome/DNA breaks in human cells. • BPAF is activated by human CYP1A1 while detoxified by SULT1A1. • Activation of aromatic hydrocarbon receptor enhances genotoxicity of BPAF. • Reactive oxygen species seems insignificant in CYP1A1-activated BPAF genotoxicity. [ABSTRACT FROM AUTHOR]

Polychlorinated biphenyls (PCBs) are persistent organic pollutants with human carcinogenicity. Many lower chlorinated and non-dioxin-like PCBs have been observed to be mutagenic following activation by human CYP2E1, while activation of dioxin-like (DL-) PCBs by this enzyme has never been evidenced. In this study, each DL-PCB was analyzed by molecular docking to human CYP2E1 protein for predicting a substrate interaction. All compounds demonstrated high affinities with the active site of human CYP2E1, binding energy being −8.7 ∼ −9.7 kcal/mol. However, most compounds demonstrated ligand-heme distances as ≥ 6.8 Å, while the values for 2,3,3′,4,4′- (PCB 105) and 2,3′,4,4′,5-pentachlorobiphenyl (PCB 118) were 5.3 and 5.4 Å, respectively (valid for electron transfer). Experimentally, both PCB 105 and 118 induced micronuclei in a V79-derived cell line engineered for expression of human CYP2E1 at low micromolar concentrations, while inactive or weakly positive in V79-Mz control cells; these effects were blocked or reduced by 1-aminobenzotriazole, a suicide CYP inhibitor. However, DL-PCBs 77, 81 and 126 were all negative in both cell lines. In a human hepatoma (C3A) cell line, PCB 105 and 118 induced micronuclei marginally, while with ethanol pretreatment (to stabilize CYP2E1) both compounds induced micronuclei efficiently, and co-exposure to trans -1,2-dichloroethylene (a selective CYP2E1 inhibitor) led to clearly negative results with both compounds. Finally, both PCB 105 and 118 induced PIG-A gene mutations in C3A cells, which was blocked by trans -1,2-dichloroethylene. In summary, in silico and experimental results consistently suggest that DL- PCBs 105 and 118 may be activated by human CYP2E1 for mutagenic activities. [ABSTRACT FROM AUTHOR]

• BPF promotes RAW264.7 macrophages M1 polarization. • The JAK2/STAT3/SOCS3 pathway is involved in BPF-promoted macrophage M1 polarization. • Estrogen receptor participates in BPF-promoted macrophage M1 polarization. As an alternative to bisphenol A (BPA), bisphenol F (BPF) has been increasingly used in manufacturing various consumer products. Exposured to BPF may lead to imbalanced immune homeostasis, yet the underlying mechanisms have not been fully elucidated. The present study was aimed to investigate the effects of BPF on macrophages and the underlying mechanism in regard to its association with estrogen receptor (ER), janus kinase 2/signal transducer and activator of transcription 3/suppressor of cytokine signaling 3 (JAK2/STAT3/SOCS3) pathway. In this study, after treatment of RAW264.7 macrophages with BPF (0, 5, 10, 20 μM), the macrophage M1 polarization was promoted, and the gene expression of M1 functional markers and pro-inflammatory cytokines was upregulated, which suggested the involvement of a vicious circle associated with chronic inflammation. Moreover, BPF facilitated SOCS3 expression in the cells in a dose-dependent manner, via activation of the JAK2/STAT3 signaling pathway, which may promote the transcription of many pro-inflammatory factors. Additionally, the above effects of BPF were blocked by either JAK2/STAT3 inhibitor AG490 (10 μM) or ER antagonist ICI 182,780 (10 μM). Taken together, the results of this study indicate that BPF promotes macrophage polarization toward pro-inflammatory M1 subtype, through activation of the ER-JAK2/STAT3/SOCS3 signaling pathway. Our finding may provide a new insight into the link between bisphenol exposure and immune dysfunction. [ABSTRACT FROM AUTHOR]

Polychlorinated biphenyls (PCBs) are persistent organic pollutants and human carcinogens. It was reported that rat CYP1A1 and catfish CYP1A can hydroxylate 3,3',4,4',5-pentachlorobiphenyl (PCB 126) and 3,3',4,4'-tetrachlorobiphenyl (PCB 77), while potential roles of other CYP1 enzymes in the metabolism of dioxin-like (DL) PCBs remain unconfirmed. In this study, three representative DL-PCBs, i.e., PCB 77, PCB 126, and 3,4,4',5-tetrachlorobiphenyl (PCB 81), were investigated on their genotoxicity in Chinese hamster V79-derived cell lines genetically engineered for the expression of human CYP1A1, 1A2 and 1B1, and in the human hepatoma C3A cell line, which endogenously expresses various CYPs. Under both 6 h/18 h and 18 h/6 h (exposure/recovery) regimes, PCB 77 and 81 induced micronuclei in V79-hCYP1B1 cells at micromolar levels, with slightly higher potency in the latter regime, while they were inactive in the parental V79-Mz cells and the V79-derived cell lines expressing human CYP1A1 and 1A2. However, PCB 126 was negative in each cell line. Likewise, PCB 77 and 81 induced micronuclei formation in C3A cells, which expressed CYP1B1. This effect was blocked by co-exposure to tetramethoxystilbene (30 nM), a selective CYP1B1 inhibitor. Immuno-fluorescent staining of centromere protein B in the micronuclei in PCB-treated cultures showed a predominance of centromere-negative micronuclei, which indicated a clastogenic effect. Moreover, all three PCBs elevated the level of γ-H2AX protein (indicating DNA double-strand breaks) in C3A cells, and these effects were blocked by tetramethoxystilbene (10 nM). This study demonstrates that some DL-PCBs are clastogenic in mammalian cells following metabolic activation by human CYP1B1. [ABSTRACT FROM AUTHOR]