Transcriptomic Dose Response Changes in Female Mouse and Rat Lungs following Chloroprene Exposure. Transcriptomic Dose Response Changes in Female Mouse and Rat Lungs following Chloroprene Exposure

ß-chloroprene (2-chloro-1,3-butadiene), a monomer used in the production of neoprene elastomers, is of regulatory interest due to the production of multi-organ tumors in mouse and rat cancer bioassays. A significant increase in female mouse lung tumors was observed at the lowest exposure concentration of 12.8 ppm while a small, but not statistically significant, increase was observed in female rats only at the highest exposure concentration of 80 ppm. The metabolism of chloroprene results in the generation of reactive epoxides and the rate of overall chloroprene metabolism is highly species dependent. To identify potential key events in the mode-of-action of chloroprene lung tumorigenesis, dose response and time course gene expression microarray measurements were made in the lungs of female mice and female rats. The gene expression changes were analyzed using both a traditional analysis of variance approach followed by pathway enrichment analysis and a pathway-based benchmark dose (BMD) analysis approach. Pathways related to glutathione biosynthesis and metabolism were the primary pathways consistent with cross-species differences in tumor incidence and transcriptional BMD values for the pathway were more similar to differences in tumor response than were estimated target tissue dose surrogates based on the total amount of chloroprene metabolized per unit mass of lung tissue per day. The closer correspondence of the transcriptional changes with the tumor response are likely due to their reflection of the overall balance between metabolic activation and detoxication reactions whereas the current tissue dose surrogate reflects only oxidative metabolism. Overall design: Female mice (B6C3F1/Crl) were exposed to chloroprene (CAS 126-99-8) by whole-body inhalation exposure at 0, 0.3, 2, 13, or 90 ppm. Exposures were performed for 6 hr/day, 5 days per week. The animals were sacrified at 5 days or 19 days (15 exposure days) post initiation of exposure. The right lung was excised and gene expression microarray analysis was performed using Affymetrix Mouse 430_2 arrays. Female rats (F344/NCrl) were exposed to chloroprene (CAS 126-99-8) by whole-body inhalation exposure at 0, 5, 30, 90, or 200 ppm. Exposures were performed for 6 hr/day, 5 days per week. The animals were sacrified at 5 days or 19 days (15 exposure days) post initiation of exposure. The right lung was excised and gene expression microarray analysis was performed using Affymetrix Rat 230_2 arrays.

β-氯丁二烯（β-chloroprene，2-氯-1,3-丁二烯）是用于生产氯丁橡胶弹性体（neoprene elastomers）的单体，因在小鼠和大鼠的致癌生物测定试验中可诱发多器官肿瘤而受到监管关注。在最低暴露浓度12.8 ppm时即可观察到雌性小鼠肺肿瘤显著升高；仅在最高暴露浓度80 ppm时，雌性大鼠才出现小幅但无统计学显著性的肿瘤数量增加。氯丁二烯的代谢过程会产生活性环氧化物，且整体代谢速率具有显著的物种依赖性。为明确氯丁二烯致肺肿瘤作用模式中的潜在关键事件，研究人员对雌性小鼠和雌性大鼠的肺部开展了剂量反应与时间序列基因表达微阵列检测。基因表达变化的分析同时采用了传统方差分析结合通路富集分析，以及基于通路的基准剂量（benchmark dose, BMD）分析方法。与谷胱甘肽（glutathione）生物合成及代谢相关的通路是与跨物种肿瘤发生率差异最一致的通路；该通路的转录组基准剂量值，相较于基于单位肺组织每日代谢氯丁二烯总量估算的靶组织剂量替代指标，更贴近肿瘤应答的种间差异。转录组变化与肿瘤应答更紧密的相关性，可能源于其反映了代谢活化与解毒反应之间的整体平衡，而当前的组织剂量替代指标仅反映了氧化代谢过程。整体实验设计：雌性B6C3F1/Crl小鼠通过全身吸入暴露接触氯丁二烯（CAS 126-99-8），暴露浓度设置为0、0.3、2、13或90 ppm，每日暴露6小时、每周5天，分别在暴露开始后5天和19天（累计15次暴露）处死动物，摘取右肺并使用Affymetrix Mouse 430_2芯片完成基因表达微阵列分析。雌性F344/NCrl大鼠通过全身吸入暴露接触氯丁二烯（CAS 126-99-8），暴露浓度设置为0、5、30、90或200 ppm，每日暴露6小时、每周5天，分别在暴露开始后5天和19天（累计15次暴露）处死动物，摘取右肺并使用Affymetrix Rat 230_2芯片完成基因表达微阵列分析。