Integrated Systems Toxicology Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA.
Toxicol Sci. 2011 Sep;123(1):80-93. doi: 10.1093/toxsci/kfr167. Epub 2011 Jul 1.
The human adrenocortical carcinoma cell line H295R is being used as an in vitro steroidogenesis screening assay to assess the impact of endocrine active chemicals (EACs) capable of altering steroid biosynthesis. To enhance the interpretation and quantitative application of measurement data in risk assessments, we are developing a mechanistic computational model of adrenal steroidogenesis in H295R cells to predict the synthesis of steroids from cholesterol (CHOL) and their biochemical response to EACs. We previously developed a deterministic model that describes the biosynthetic pathways for the conversion of CHOL to steroids and the kinetics for enzyme inhibition by the EAC, metyrapone (MET). In this study, we extended our dynamic model by (1) including a cell proliferation model supported by additional experiments and (2) adding a pathway for the biosynthesis of oxysterols (OXY), which are endogenous products of CHOL not linked to steroidogenesis. The cell proliferation model predictions closely matched the time-course measurements of the number of viable H295R cells. The extended steroidogenesis model estimates closely correspond to the measured time-course concentrations of CHOL and 14 adrenal steroids both in the cells and in the medium and the calculated time-course concentrations of OXY from control and MET-exposed cells. Our study demonstrates the improvement of the extended, more biologically realistic model to predict CHOL and steroid concentrations in H295R cells and medium and their dynamic biochemical response to the EAC, MET. This mechanistic modeling capability could help define mechanisms of action for poorly characterized chemicals for predictive risk assessments.
人肾上腺皮质癌细胞系 H295R 被用作体外类固醇生成筛选测定法，以评估能够改变类固醇生物合成的内分泌活性化学物质 (EAC) 的影响。为了增强风险评估中测量数据的解释和定量应用，我们正在开发一种 H295R 细胞肾上腺类固醇生成的机制计算模型，以预测胆固醇 (CHOL) 合成类固醇及其对 EAC 的生化反应。我们之前开发了一个确定性模型，描述了 CHOL 转化为类固醇的生物合成途径以及 EAC、美替拉酮 (MET) 对酶抑制的动力学。在这项研究中，我们通过 (1) 包括一个由额外实验支持的细胞增殖模型，以及 (2) 添加一个合成氧化固醇 (OXY) 的途径来扩展我们的动态模型，OXY 是 CHOL 的内源性产物，与类固醇生成无关。细胞增殖模型的预测与 H295R 细胞存活数量的时间过程测量非常吻合。扩展的类固醇生成模型估计与 CHOL 和 14 种肾上腺类固醇在细胞和培养基中的测量时间过程浓度以及从对照和 MET 暴露细胞计算的 OXY 的时间过程浓度非常吻合。我们的研究表明，扩展的、更具生物学现实性的模型在预测 H295R 细胞和培养基中的 CHOL 和类固醇浓度及其对 EAC、MET 的动态生化反应方面得到了改进。这种机制建模能力可以帮助定义作用机制不明确的化学物质的预测风险评估。
