Project description:The constitutive androstane receptor (CAR) and the pregnane X receptor (PXR) are closely related nuclear receptors involved in drug metabolism and play important roles in the mechanism of phenobarbital (PB)-induced rodent nongenotoxic hepatocarcino- genesis. Here, we have used a humanized CAR/PXR mouse model to examine potential species differences in receptor-dependent mechanisms underlying liver tissue molecular responses to PB. Early and late transcriptomic responses to sustained PB exposure were investigated in liver tissue from double knock-out CAR and PXR (CARKO -PXRKO ), double humanized CAR and PXR (CARh - PXRh), and wild-type C57BL/6 mice. Wild-type and CARh-PXRh mouse livers exhibited temporally and quantitatively similar tran- scriptional responses during 91 days of PB exposure including the sustained induction of the xenobiotic response gene Cyp2b10, the Wnt signaling inhibitor Wisp1, and noncoding RNA biomarkers from the Dlk1-Dio3 locus. Transient induction of DNA replication (Hells, Mcm6, and Esco2) and mitotic genes (Ccnb2, Cdc20, and Cdk1) and the proliferation-related nuclear antigen Mki67 were ob- served with peak expression occurring between 1 and 7 days PB ex- posure. All these transcriptional responses were absent in CARKO- PXRKO mouse livers and largely reversible in wild-type and CARh - PXRh mouse livers following 91 days of PB exposure and a subse- quent 4-week recovery period. Furthermore, PB-mediated upregu- lation of the noncoding RNA Meg3, which has recently been associ- ated with cellular pluripotency, exhibited a similar dose response and perivenous hepatocyte-specific localization in both wild-type and CARh-PXRh mice. Thus, mouse livers coexpressing human CAR and PXR support both the xenobiotic metabolizing and the proliferative transcriptional responses following exposure to PB. 13-week oral (drinking water) investigative phenobarbital study in male C57BL/6 wild type, CAR/PXR knockout and humanized CAR/PXR mice with a 4 week recovery period

Project description:The development of a biodosimetric assay based on the combined gene expression analysis of ex vivo-irradiated human peripheral blood (PB) and humans treated with total body irradiation has been developed. Gene expression profile signature of human radiation injury into a rapid and high-throughput chemical ligation-dependent probe amplification assay (CLPA) has been shown to discriminate 6 radiation dose levels in human PB. Candidate gene lists were first developed assaying human ex vivo and human TBI samples on the Affymetrix platform. For the Ex Vivo samples, healthy consented adult donor was randomly assigned to a radiation group and labeled with the target dose of 0 cGy, 150 cGy, 300 cGy, or 600 cGy. In addition to the radiation exposures, the samples were also treated with either no treatment, GCSF, or LPS at time points 6 hours and 24 hours. Radiation expire times from the Cs137 irradiator were calculated to achieve target doses specific for tubes filled with blood and inserted in the roaring test tube holder. The dose rate was 480 cGy/min for the duration of the study. The healthy donors were enrolled to participate in this study following a protocol to collect PB samples that was previously approved by the Duke University Institutional Review Board. For the TBI samples, adult patients, ages 21 to 66, were evaluated at the Duke University Adult Bone Marrow Transplantation Program enrolled in a Duke IRB-approved protocol to collect PB prior to and post TBI conditioning. With approval from the Duke University Institutional Review Board (IRB), between 5-12 mL of peripheral blood was collected from consented patients prior to and 6 hours following TBI with 150-200 cGy as part of their pre-transplantation conditioning. All patients receiving non-myeloablative conditioning were treated with 200 cGy of TBI from a linear accelerator at a dose rate of 20 cGy/min. All patients who underwent TBI-based myeloablative allogeneic or autologous stem-cell transplantation received radiation fractionated at 150 cGy per fraction at 20 cGy/min. All patients had PB collected (50 ml) prior to and 6 hours following exposure to either 200 cGy or 150 cGy radiation treatment. The dose exposure for TBI patients used in this study were 0 cGy, 150 cGy, 450 cGy and 1050 cGy at 0, 6, 30 and 78 hours post irradiation. Total RNA was extracted and assayed on the Affymetrix platform.

Project description:BACKGOUND: Drinking water can be contaminated with pharmaceuticals. However, it is uncertain whether this contamination can have harmful consequences for the liver, especially in the context of obesity. OBJECTIVES: To determine whether chronic, low dose exposure to pharmaceuticals could have deleterious effects in livers of lean and obese mice. METHODS: Lean and ob/ob male mice (5-week-old) were treated for 4 months with a mixture of 11 drugs (acetaminophen, caffeine, carbamazepine, cotinine, diclofenac, erythromycin, ibuprofen, phenazone, roxithromycin, salicylic acid and sulfamethoxazole) provided in drinking water at a concentration of 1 mg/L (for each drug). At the end of the treatment, investigations were performed in liver and plasma. RESULTS: Some liver and plasma abnormalities were observed in ob/ob mice treated with the cocktail containing 1 mg/L of each drug. For this dosage, a gene expression analysis by microarray showed altered expression of circadian genes (e.g. Bmal1, Dbp, Cry1) in lean and obese mice. RT-qPCR analyses carried out in all groups of animals indicated that expression of 8 different circadian genes was significantly modified in a dose-dependent manner. For some genes, a significant modification was observed for dosages as low as 100-1,000 ng/L. Drug mixture and obesity presented an additive effect on circadian gene expression. These data were confirmed in an independent study performed in female mice. CONCLUSIONS: Chronic, low dose exposure to pharmaceuticals disturbed hepatic expression of circadian genes, especially in obese mice. Because some of the 11 drugs can be found in the drinking water at such concentrations (e.g. acetaminophen, carbamazepine, ibuprofen) our data could be relevant in environmental toxicology, in particular for obese individuals exposed to these contaminants. C57BL/6J lean and ob/ob male mice (5-week-old) were treated for 4 months with a mixture of 11 drugs provided in drinking water at a concentration of 1 mg/L (for each drug). 4 groups were designed: untreated versus treated WT and ob/ob mice (n=6 mice per group).

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Whole blood gene expression in female Balb/c mice following 2-week Pb exposure and subsequent 2-week recovery period

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