Potency ranking of per- and polyfluoroalkyl substances using high-throughput transcriptomic analysis of human liver spheroids

Per- and polyfluoroalkyl substances (PFAS) are some of the most prominent organic contaminants in human blood. Although the toxicological implications of human exposure to perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are well established, data on lesser-understood PFAS are limited. New approach methodologies (NAMs) that apply bioinformatic tools to high-throughput data are being increasingly considered to inform risk assessment for data-poor chemicals. The aim of this study was to compare the potencies (i.e., benchmark concentrations: BMCs) of PFAS in primary human liver microtissues (3D spheroids) using high-throughput transcriptional profiling. Gene expression changes were measured using TempO-seq, a templated, multiplexed RNA-sequencing platform. Spheroids were exposed for 1 or 10 days to increasing concentrations of 23 PFAS in three subgroups: carboxylates (PFCAs), sulfonates (PFSAs), and fluorotelomers and sulfonamides. PFCAs and PFSAs exhibited trends toward increased transcriptional potency with carbon chain-length. Specifically, longer-chain compounds (7 to 10 carbons) were more likely to induce changes in gene expression and have lower transcriptional BMCs. The combined high-throughput transcriptomic and bioinformatic analyses support the capability of NAMs to efficiently assess the effects of PFAS in liver microtissues. The data enable potency ranking of PFAS for human liver cell spheroid cytotoxicity and transcriptional changes, and assessment of in vitro transcriptomic points of departure. These data improve our understanding of the possible health effects of PFAS and will be used to inform read-across for human health risk assessment.

High-throughput transcriptomics and benchmark concentration modeling for potency ranking of per- and polyfluoroalkyl substances (PFAS) in exposed human liver cell spheroids

Per- and polyfluoroalkyl substances (PFAS) are some of the most prominent organic contaminants in human blood. Although the toxicological implications from human exposure to perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are well established, data on lesser-understood PFAS are limited. New approach methodologies (NAMs) that apply bioinformatic tools to high-throughput data are being increasingly considered to inform risk assessment for data-poor chemicals. The aim of this investigation was to identify biological response potencies (i.e., benchmark concentrations: BMCs) following PFAS exposures to inform read-across for risk assessment of data-poor PFAS. Gene expression changes were measured in primary human liver cell microtissues (i.e., 3D spheroids) after 1-day and 10-day exposures to increasing concentrations of 23 PFAS. The cells were treated with four subgroups of PFAS: carboxylates (PFCAs), sulfonates (PFSAs), fluorotelomers, and sulfonamides. An established pipeline to identify differentially expressed genes and transcriptomic BMCs was applied. We found that both PFCAs and PFSAs exhibited a trend toward increased transcriptional changes with carbon chain-length. Specifically, longer-chain compounds (7 to 10 carbons) were more likely to induce changes in gene expression, and have lower transcriptional BMCs. The combined high-throughput transcriptomic and bioinformatic analyses supports the capability of NAMs to efficiently assess the effects of PFAS in liver microtissues. The data enable potency ranking of PFAS for human liver cell spheroid cytotoxicity and transcriptional changes, and assessment of in vitro transcriptomic points of departure. These data improve our understanding of the health effects of PFAS and will be used to inform read-across for human health risk assessment.

In Silico Exploration of Molecular Mechanism and Potency Ranking of Clinically Oriented Drugs for Inhibiting SARS-CoV-2’s Main Protease

<p>Currently, the new coronavirus disease 2019 (COVID-19) is a global pandemic without any well calibrated treatment. To inactivate the SARS-CoV-2 virus that causes COVID-19, the main protease (Mpro) that performs key biological functions in the virus has been the focus of extensive studies. With the fast-response experimental efforts, the crystal structures of Mpro of the SARS-CoV-2 virus have just become available recently. Herein, we theoretically investigated the binding mechanism between the Mpro's pocket and various marketed drug molecules being tested in clinics to fight COVID-19 that show promising outcomes. Combining all existing experiment results with our computational ones, we revealed an important ligand-binding mechanism for the Mpro that the binding stability of a ligand inside the Mpro pocket can be significantly improved if the partial ligand occupies the so-called "anchor" site of the Mpro. Along with the high-potent drugs/molecules (such as nelfinavir and curcumin) revealed in this study, the newly discovered binding mechanism paves the way for further optimizations and designs of Mpro's inhibitors with a high binding affinity. </p>

In Silico Exploration of Molecular Mechanism and Potency Ranking of Clinically Oriented Drugs for Inhibiting SARS-CoV-2’s Main Protease

<p>Currently, the new coronavirus disease 2019 (COVID-19) is a global pandemic without any well calibrated treatment. To inactivate the SARS-CoV-2 virus that causes COVID-19, the main protease (Mpro) that performs key biological functions in the virus has been the focus of extensive studies. With the fast-response experimental efforts, the crystal structures of Mpro of the SARS-CoV-2 virus have just become available recently. Herein, we theoretically investigated the binding mechanism between the Mpro's pocket and various marketed drug molecules being tested in clinics to fight COVID-19 that show promising outcomes. Combining all existing experiment results with our computational ones, we revealed an important ligand-binding mechanism for the Mpro that the binding stability of a ligand inside the Mpro pocket can be significantly improved if the partial ligand occupies the so-called "anchor" site of the Mpro. Along with the high-potent drugs/molecules (such as nelfinavir and curcumin) revealed in this study, the newly discovered binding mechanism paves the way for further optimizations and designs of Mpro's inhibitors with a high binding affinity. </p>