Potential Human Health Hazard of Post-Hurricane Harvey Sediments in Galveston Bay and Houston Ship Channel: A Case Study of Using In Vitro Bioactivity Data to Inform Risk Management Decisions

Natural and anthropogenic disasters may be associated with redistribution of chemical contaminants in the environment; however, current methods for assessing hazards and risks of complex mixtures are not suitable for disaster response. This study investigated the suitability of in vitro toxicity testing methods as a rapid means of identifying areas of potential human health concern. We used sediment samples (n = 46) from Galveston Bay and the Houston Ship Channel (GB/HSC) areas after hurricane Harvey, a disaster event that led to broad redistribution of chemically-contaminated sediments, including deposition of the sediment on shore due to flooding. Samples were extracted with cyclohexane and dimethyl sulfoxide and screened in a compendium of human primary or induced pluripotent stem cell (iPSC)-derived cell lines from different tissues (hepatocytes, neuronal, cardiomyocytes, and endothelial) to test for concentration-dependent effects on various functional and cytotoxicity phenotypes (n = 34). Bioactivity data were used to map areas of potential concern and the results compared to the data on concentrations of polycyclic aromatic hydrocarbons (PAHs) in the same samples. We found that setting remediation goals based on reducing bioactivity is protective of both “known” risks associated with PAHs and “unknown” risks associated with bioactivity, but the converse was not true for remediation based on PAH risks alone. Overall, we found that in vitro bioactivity can be used as a comprehensive indicator of potential hazards and is an example of a new approach method (NAM) to inform risk management decisions on site cleanup

Enantiomeric characterization of herbicide lactofen: Enantioseparation, absolute configuration assignment and enantioselective activity and toxicity

Chiral herbicides consist of two or more enantiomers, which usually differ in their biological properties and behave enantioselectively in biochemical process. Scant studies have been published in the past decades to characterize the enantiomers of herbicide lactofen. In this study, a laboratory method was developed to prepare the lactofen enantiomers using normal phase high performance liquid chromatography with an AD-H column, and μg level production yield was achieved in a single run. The two separated enantiomers had purity of ≫99%, with their absolute configurations assigned by experimental and calculated electronic and vibrational circular dichroism. Spectral analyses including semi-empirical rules as well as comparisons with the results of quantum chemical calculations confirmed the molecular configurations of R-lactofen and S-lactofen, in this elution order. The enantioselective bioactivity toward weed (Echinochloa crusgalli) and toxicity toward aquatic algae (Microcystis aeruginosa) was assessed by measuring their growth rates after the treatments with lactofen enantiomers and racemate. The results showed that R-lactofen affected E. crusgalli more severely, while S-lactofen was more toxic to algae. Using active enantiomer instead of racemate may be more efficient and safe. Therefore, a more comprehensive understanding of the behaviors of chiral enantiomers is a need to improve activity and risk assessment and regulations of chiral compounds. Our work will be helpful to easily prepare single enantiomers from racemic mixtures and to establish effective absolute configurations of the enantiomers

Enantiomeric characterization of herbicide lactofen: Enantioseparation, absolute configuration assignment and enantioselective activity and toxicity

Chiral herbicides consist of two or more enantiomers, which usually differ in their biological properties and behave enantioselectively in biochemical process. Scant studies have been published in the past decades to characterize the enantiomers of herbicide lactofen. In this study, a laboratory method was developed to prepare the lactofen enantiomers using normal phase high performance liquid chromatography with an AD-H column, and μg level production yield was achieved in a single run. The two separated enantiomers had purity of ≫99%, with their absolute configurations assigned by experimental and calculated electronic and vibrational circular dichroism. Spectral analyses including semi-empirical rules as well as comparisons with the results of quantum chemical calculations confirmed the molecular configurations of R-lactofen and S-lactofen, in this elution order. The enantioselective bioactivity toward weed (Echinochloa crusgalli) and toxicity toward aquatic algae (Microcystis aeruginosa) was assessed by measuring their growth rates after the treatments with lactofen enantiomers and racemate. The results showed that R-lactofen affected E. crusgalli more severely, while S-lactofen was more toxic to algae. Using active enantiomer instead of racemate may be more efficient and safe. Therefore, a more comprehensive understanding of the behaviors of chiral enantiomers is a need to improve activity and risk assessment and regulations of chiral compounds. Our work will be helpful to easily prepare single enantiomers from racemic mixtures and to establish effective absolute configurations of the enantiomers

Are Nutrient Stresses Associated with Enantioselectivity of the Chiral Herbicide Imazethapyr in Arabidopsis thaliana?

Plant growth can be inhibited by herbicides and is strongly limited by the availability of nutrients, which can influence human health through the food chain. Until now, however, cross talk between the enantioselectivity of herbicides and nutrient stresses has been poorly understood. We analyzed trace element and macroelement contents in shoots of Arabidopsis thaliana treated by the chiral herbicide imazethapyr (IM) and observed that multiple-nutrient stress (trace elements Mn, Cu, and Fe and macroelements P, K, Ca, and Mg) was enantioselective. The (<i>R</i>)-IM treatments resulted in Mn 23.37%, Cu 63.53%, P 30.61%, K 63.70%, Ca 34.32%, and Mg 36.14% decreases compared with the control. Interestingly, it was also found that herbicidally active (<i>R</i>)-IM induced notable aggregation of nutrient elements in leaves and roots compared with the control and (<i>S</i>)-IM. Through gene expression analyses, it was found that herbicidally active (<i>R</i>)-IM induced the up- or down-regulation of genes involved in the transport of nutrient elements. We propose that (<i>R</i>)-IM affected the uptake and translocation of nutrient elements in <i>A. thaliana</i>, which destroyed the balance of nutrient elements in the plant. This finding reminds us to reconsider the effect of nutrient stresses in risk assessment of herbicides

Enantioselective Phytotoxicity of Dichlorprop to <i>Arabidopsis thaliana</i>: The Effect of Cytochrome P450 Enzymes and the Role of Fe

The ecotoxicology effects of chiral herbicides have long been recognized and have drawn increasing attention. The toxic mechanisms of herbicides in plants are involved in production of reactive oxygen species (ROS) and cause damage to target enzymes, but the relationship between these two factors in the enantioselectivity of chiral herbicides has rarely been investigated. Furthermore, even though cytochromes P450 enzymes (CYP450s) have been related to the phytotoxicity of herbicides, their roles in the enantioselectivity of chiral herbicides have yet to be explored. To solve this puzzle, the CYP450s suicide inhibitor 1-aminobenzotriazole (ABT) was added to an exposure system made from dichlorprop (DCPP) enantiomers in the model plant <i>Arabidopsis thaliana</i>. The results indicated that different phytotoxicities of DCPP enantiomers by causing oxidative stress and acetyl-CoA carboxylase (ACCase) damage were observed in the presence and the absence of ABT. The addition of ABT decreased the toxicity of (<i>R</i>)-DCPP but was not significantly affected that of (<i>S</i>)-DCPP, resulting in smaller differences between enantiomers. Furthermore, profound differences were also observed in Fe uptake and distribution, exhibiting different distribution patterns in <i>A. thaliana</i> leaves exposed to DCPP and ABT, which helped bridge the relationship between ROS production and target enzyme ACCase damage through the function of CYP450s. These results offer an opportunity for a more-comprehensive understanding of chiral herbicide action mechanism and provide basic evidence for risk assessments of chiral herbicides in the environment

Human in vitro vascularized micro-organ and micro-tumor models are reproducible organ-on-a-chip platforms for studies of anticancer drugs

Angiogenesis is a complex process that is required for development and tissue regeneration and it may be affected by many pathological conditions. Chemicals and drugs can impact formation and maintenance of the vascular networks; these effects may be both desirable (e.g., anti-cancer drugs) or unwanted (e.g., side effects of drugs). A number of in vivo and in vitro models exist for studies of angiogenesis and endothelial cell function, including organ-on-a-chip microphysiological systems. An arrayed organ-on-a-chip platform on a 96-well plate footprint that incorporates perfused microvessels, with and without tumors, was recently developed and it was shown that survival of the surrounding tissue was dependent on delivery of nutrients through the vessels. Here we describe a technology transfer of this complex microphysiological model between laboratories and demonstrate that reproducibility and robustness of these tissue chip-enabled experiments depend primarily on the source of the endothelial cells. The model was highly reproducible between laboratories and was used to demonstrate the advantages of the perfusable vascular networks for drug safety evaluation. As a proof-of-concept, we tested Fluorouracil (1-1,000 μM), Vincristine (1-1,000 nM), and Sorafenib (0.1-100 μM), in the perfusable and non-perfusable micro-organs, and in a colon cancer-containing micro-tumor model. Tissue chip experiments were compared to the traditional monolayer cultures of endothelial or tumor cells. These studies showed that human in vitro vascularized micro-organ and micro-tumor models are reproducible organ-on-a-chip platforms for studies of anticancer drugs. The data from the 3D models confirmed advantages of the physiological environment as compared to 2D cell cultures. We demonstrated how these models can be translated into practice by verifying that the endothelial cell source and passage are critical elements for establishing a perfusable model