Synergistic and antagonistic interactions among organic and metallic components of the ambient particulate matter (PM) for the cytotoxicity measured by Chinese hamster ovary cells

• Published in: The Science of the total environment Vol. 736; p. 139511
• Main Authors: Wang, Yixiang, Puthussery, Joseph V., Yu, Haoran, Verma, Vishal
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 20.09.2020
• Subjects: Chinese hamster ovary (CHO) cells; Cytotoxicity; Humic-like substances; Interactions; Metals; Mixture toxicity index; Cytotoxicity; Humic-like substances; Interactions; Chinese hamster ovary (CHO) cells; Mixture toxicity index; Metals
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.139511

Although PM2.5 toxicity is known to be related to its chemical composition, the effect of interactions among various particles' components on the toxicity is not well explored. To understand these interactions, especially metals and organic compounds on PM2.5 cytotoxicity, we chose several redox-active substances known to be present in the ambient particles such as metals (Cu, Fe, and Mn) and quinones [9,10-phenanthraquinone (PQ), 1,2-naphthoquinone (1,2-NQ), 1,4-naphthoquinone (1,4-NQ), and 5-hydroxy-1,4-naphthoquinone (5,H-1,4-NQ)]. Cytotoxicity was assessed through a Chinese hamster ovary (CHO) cells assay and expressed by a median lethal concentration (LC50). Two methods were employed to assess the interactions. In the first method, we tested the impact of nontoxic level of a component on the LC50 of other components. In the second method, we mixed two components in different concentration ratios to expose the cells and calculated a mixture toxicity index (MTI). MTI is a composite value to quantify the nature of interactions such that the interactions are considered synergistic when MTI > 1, additive when 0 < MTI ≤ 1 and antagonistic when MTI < 0. The interactions between quinones and metals were largely synergistic by both methods. To further assess the environmental relevance of these mixtures, we extracted organic compounds termed as water-soluble Humic-like substances (HULIS) from real ambient PM samples and mixed them with individual metals. A similar pattern, as observed from the interaction of quinones and metals, was found. Moreover, the interactions became more synergistic as the relative concentration of metals with respect to water-soluble HULIS was decreased in these mixtures. With environmentally relevant mass concentration ratios of organics to metals (75–7500), the interactions were strongly synergistic (MTI = 1–115). These results indicate the importance of incorporating the interaction among various PM components for estimating the net toxicity of ambient PM2.5. [Display omitted] •We systematically explored the effect of interaction among various PM2.5 components on the cytotoxicity.•The interactions between metals and organic compounds for the cytotoxicity appear to be concentration-dependent.•Under the environmentally-relevant concentration ratios, the interactions of metals and organic compounds are synergistic.•To estimate the overall toxicity of PM2.5, the interaction effects among different PM components should be considered.