Benchmarking Water Quality from Wastewater to Drinking Waters Using Reduced Transcriptome of Human Cells

One of the major challenges in environmental science is monitoring and assessing the risk of complex environmental mixtures. In vitro bioassays with limited key toxicological end points have been shown to be suitable to evaluate mixtures of organic pollutants in wastewater and recycled water. Omics approaches such as transcriptomics can monitor biological effects at the genome scale. However, few studies have applied omics approach in the assessment of mixtures of organic micropollutants. Here, an omics approach was developed for profiling bioactivity of 10 water samples ranging from wastewater to drinking water in human cells by a reduced human transcriptome (RHT) approach and dose-response modeling. Transcriptional expression of 1200 selected genes were measured by an Ampliseq technology in two cell lines, HepG2 and MCF7, that were exposed to eight serial dilutions of each sample. Concentration-effect models were used to identify differentially expressed genes (DEGs) and to calculate effect concentrations (ECs) of DEGs, which could be ranked to investigate low dose response. Furthermore, molecular pathways disrupted by different samples were evaluated by Gene Ontology (GO) enrichment analysis. The ability of RHT for representing bioactivity utilizing both HepG2 and MCF7 was shown to be comparable to the results of previous in vitro bioassays. Finally, the relative potencies of the mixtures indicated by RHT analysis were consistent with the chemical profiles of the samples. RHT analysis with human cells provides an efficient and cost-effective approach to benchmarking mixture of micropollutants and may offer novel insight into the assessment of mixture toxicity in water.

环境科学领域的核心挑战之一，在于对复杂环境混合污染物的风险开展监测与评估。仅针对关键毒理学终点的体外生物测试（in vitro bioassays）已被证实可用于评估废水与再生水中的有机污染物混合体系。转录组学（transcriptomics）等组学方法能够在基因组层面监测生物效应，然而目前鲜有研究将组学方法应用于有机微污染物混合体系的风险评估。本研究通过简化人类转录组（reduced human transcriptome, RHT）方法与剂量反应建模，开发了一种组学分析手段，用于在人类细胞中表征10份涵盖废水至饮用水范围的水样的生物活性；采用Ampliseq技术，对经8个系列稀释浓度的每份样品处理后的两种细胞系（HepG2与MCF7）中1200个选定基因的转录表达水平进行了检测；利用浓度效应模型识别差异表达基因（differentially expressed genes, DEGs），并计算DEGs的效应浓度（effect concentrations, ECs），通过对ECs进行排序以探究低剂量下的生物响应特征。此外，本研究通过基因本体（Gene Ontology, GO）富集分析，评估了不同水样所干扰的分子通路。研究证实，利用HepG2与MCF7细胞开展的RHT分析所表征的生物活性，与既往体外生物测试的结果具有可比性；最终，RHT分析所揭示的混合污染物相对效力，与各样品的化学组分特征保持一致。基于人类细胞的RHT分析方法，为微污染物混合体系的基准值构建提供了一种高效且经济的手段，有望为水环境混合污染物毒性评估提供全新的研究视角。