Toxicological sciences : an official journal of the Society of Toxicology
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Comparative Study
RNA-Seq provides new insights in the transcriptome responses induced by the carcinogen benzo[a]pyrene.
Whole-genome transcriptome measurements are pivotal for characterizing molecular mechanisms of chemicals and predicting toxic classes, such as genotoxicity and carcinogenicity, from in vitro and in vivo assays. In recent years, deep sequencing technologies have been developed that hold the promise of measuring the transcriptome in a more complete and unbiased manner than DNA microarrays. Here, we applied this RNA-seq technology for the characterization of the transcriptomic responses in HepG2 cells upon exposure to benzo[a]pyrene (BaP), a well-known DNA damaging human carcinogen. ⋯ The biological function(s) of these isoforms remain for the time being unknown. Finally, we demonstrate that RNA-seq enables the investigation of allele-specific gene expression, although no changes could be observed. Our results provide evidence that RNA-seq is a powerful tool for toxicology, which, compared with microarrays, is capable of generating novel and valuable information at the transcriptome level for characterizing deleterious effects caused by chemicals.
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Subchronic exposure to arsenic increases the incidence of human cancers such as skin, lung, colon, and rectal cancer. The mechanism for arsenic-induced tumorigenesis is still not clear. It is generally believed that DNA damage and genomic instability, generated by arsenic-promoted oxidative stress, account largely for this process. ⋯ Contrarily, inhibition of autophagy activity decreases mitochondria turnover and enhances arsenic-induced ROS generation and cell transformation. In addition, the mammalian target of rapamycin signaling pathway is involved in arsenic-mediated autophagy activation. Our results suggest that autophagy is a cell self-protective mechanism against arsenic-induced cell transformation.
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Glutamate excitotoxicity plays a key role in the etiology of a variety of neurological, psychiatric, and neurodegenerative disorders. The goal of this study was to investigate spatiotemporal distribution in the brain and cerebrospinal fluid (CSF) concentrations of ubiquitin C-terminal hydrolase-1 (UCH-L1), glial fibrillary acidic protein (GFAP), αII-spectrin breakdown products (SBDP150, SBDP145, and SBDP120), and their relationship to neuropathology in an animal model of kainic acid (KA) excitotoxicity. Triple fluorescent labeling and Fluoro-Jade C staining revealed a reactive gliosis in brain and specific localization of degenerating neurons in hippocampus and entorhinal cortex of KA-treated rats. ⋯ The temporal increase in CSF biomarkers correlated with brain tissue distribution and neurodegeneration. This study provided evidence supporting the use of CSF levels of glial and neuronal protein biomarkers to assess neurotoxic damage in preclinical animal models that could prove potentially translational to the clinic. The molecular nature of these biomarkers can provide critical information on the underlying mechanisms of neurotoxicity that might facilitate the development of novel drugs and allow physicians to monitor drug safety.
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2,3,5-Tris(glutathion-S-yl)hydroquinone (TGHQ), a metabolite of benzene, catalyzes the generation of reactive oxygen species (ROS) and caspase-dependent apoptosis in human promyelocytic leukemia (HL-60) cells. We now report that TGHQ induces severe DNA damage, as evidenced by DNA ladder formation and H2AX phosphorylation. The subsequent activation of the DNA nick sensor enzyme, poly(ADP-ribose) polymerase-1 (PARP-1), leads to the rapid depletion of ATP and NAD and the concomitant formation of poly(ADP-ribosylated) proteins (PARs). ⋯ In summary, TGHQ-induced apoptosis of HL-60 cells is accompanied by PARP-1, caspase activation, and AIF nuclear translocation. TGHQ-induced apoptosis appears to primarily occur via engagement of the mitochondrial-mediated pathway in a process amenable to PARP inhibition. Residual cell death in the presence of PJ-34 is likely mediated via the extrinsic apoptotic pathway.
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Deoxynivalenol (DON) and T-2 toxin commonly affect cells of the immune system and cause inflammation and apoptosis. Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway is highly associated with inflammatory process and apoptosis and is worth investigating its role when cells were exposed to trichothecenes. The results showed that DON and T-2 upregulated the messenger RNA (mRNA) expressions of interleukin (IL)-6, IL-1β, tumor necrosis factor-α, JAK1-2, STAT1-3, and suppressors of cytokine signaling members and activated the tyrosine phosphorylation of STAT1 and STAT3 with a dose-dependent manner in RAW264.7 cells. ⋯ After exposing to DON and T-2 toxin, cells exhibited G2/M and G0/G1 phase arrest, respectively. The increased mRNA expressions of STAT target genes p21 and cyclin D1 for DON and the increases in p21 mRNA and the decreases in cyclin D1 for T-2 toxin were observed. These results demonstrated for the first time that the activation of JAK/STAT might be a critical mediator to induce the inflammatory response and apoptosis in macrophage in response to trichothecenes.