The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) protein binds angiotensin-converting enzyme 2 as its primary infection mechanism. Interactions between S and endogenous proteins occur after infection but are not well understood. We profiled binding of S against >9000 human proteins and found an interaction between S and human estrogen receptor α (ERα). Using bioinformatics, supercomputing, and experimental assays, we identified a highly conserved and functional nuclear receptor coregulator (NRC) LXD-like motif on the S2 subunit. In cultured cells, S DNA transfection increased ERα cytoplasmic accumulation, and S treatment induced ER-dependent biological effects. Non-invasive imaging in SARS-CoV-2–infected hamsters localized lung pathology with increased ERα lung levels. Postmortem lung experiments from infected hamsters and humans confirmed an increase in cytoplasmic ERα and its colocalization with S in alveolar macrophages. These findings describe the discovery of a S-ERα interaction, imply a role for S as an NRC, and advance knowledge of SARS-CoV-2 biology and coronavirus disease 2019 pathology.

In vitro methods which incorporate metabolic capability into the assays allow us to assess the activity of metabolites from their parent compounds. These methods can be applied into high-throughput screening (HTS) platforms, thereby increasing the speed to identify compounds that become active via the metabolism process. HTS was originally used in the pharmaceutical industry and now is also used in academic settings to evaluate biological activity and/or toxicity of chemicals. Although most chemicals are metabolized in our body, many HTS assays lack the capability to determine compound activity via metabolism. To overcome this problem, several in vitro metabolic methods have been applied to an HTS format. In this review, we describe in vitro metabolism methods and their application in HTS assays, as well as discuss the future perspectives of HTS with metabolic activity. Each in vitro metabolism method has advantages and disadvantages. For instance, the S9 mix has a full set of liver metabolic enzymes, but it displays high cytotoxicity in cell-based assays. In vitro metabolism requires liver fractions or the use of other metabolically capable systems, including primary hepatocytes or recombinant enzymes. Several newly developed in vitro metabolic methods, including HepaRG cells, three-dimensional (3D) cell models, and organ-on-a-chip technology, will also be discussed. These newly developed in vitro metabolism approaches offer significant progress in dissecting biological processes, developing drugs, and making toxicology studies quicker and more efficient.

Traditional in vitro intestinal model systems frequently fail to accurately replicate human intestinal physiology for absorption, distribution, metabolism, excretion, and toxicity (ADMET) assessments. These limitations, coupled with the growing demand for faster drug discovery and high-throughput screening capabilities, have refined more physiologically relevant models. Recent advancements have led to the development of cell-based intestinal systems that better reflect in vivo conditions, ranging from monolayer and coculture models to complex three-dimensional (3-D) cell culture systems, microfluidic devices, and bioengineered models. This review provides a comprehensive overview of current progress, ongoing challenges, and future directions in developing and applying human in vitro intestinal models for chemical testing.

Autophagy is a cellular degradation process that plays a critical role in maintaining homeostasis and preventing stress-induced damage, making it a promising therapeutic target for cancer and neurodegenerative diseases. In this study, we utilized mouse embryonic fibroblasts expressing GFP-labeled microtubule-associated protein 1 light chain 3, a widely used biomarker of autophagy activation, to screen 3733 clinically approved or investigational drugs using a high-throughput and high-content screening platform. From the primary screening, 117 compounds were identified as potential autophagy inducers. Subsequent confirmation studies narrowed this group to 5 previously uncharacterized autophagy-inducing candidates for further investigation. Follow-up studies assessed the mechanisms underlying autophagy modulation by these compounds, with a focus on key pathways such as mechanistic target of rapamycin inhibition, endoplasmic reticulum stress activation, and p53 activation. To further explore their therapeutic potential in cancer, we conducted an angiogenesis inhibition assay. This study successfully identified several autophagy inducers that may be repurposed for the treatment of cancer, highlighting their potential for future therapeutic development. SIGNIFICANT STATEMENT: This study identifies novel autophagy inducers from high-throughput screening of approved and investigational drugs. The findings highlight key pathways such as mechanistic target of rapamycin inhibition and endoplasmic reticulum stress activation, and demonstrate the ability of these compounds to inhibit angiogenesis, suggesting their potential for repurposing in cancer therapy.