Screening ToxCast™ for Chemicals That Affect Cholesterol Biosynthesis: Studies in Cell Culture and Human Induced Pluripotent Stem Cell-Derived Neuroprogenitors

BACKGROUND: Changes in cholesterol metabolism are common hallmarks of neurodevelopmental pathologies. A diverse array of genetic disorders of cholesterol metabolism support this claim as do multiple lines of research that demonstrate chemical inhibition of cholesterol biosynthesis compromises neurodevelopment. Recent work has revealed that a number of commonly used pharmaceuticals induce changes in cholesterol metabolism that are similar to changes induced by genetic disorders with devastating neurodevelopmental deficiencies. OBJECTIVES: We tested the hypothesis that common environmental toxicants may also impair cholesterol metabolism and thereby possibly contribute to neurodevelopmental toxicity. METHODS: Using high-throughput screening with a targeted lipidomic analysis and the mouse neuroblastoma cell tine, Neuro-2a, the ToxCast (TM) chemical library was screened for compounds that impact sterol metabolism. Validation of chemical effects was conducted by assessing cholesterol biosynthesis in human induced pluripotent stem cell (hiPSC)-derived neuroprogenitors using an isotopically labeled cholesterol precursor and by monitoring product formation with UPLC-MS/MS. RESULTS: Twenty-nine compounds were identified as validated lead-hits, and four were prioritized for further study (endosulfan sulfate, tributyltin chloride, fenpropimorph, and spiroxamine). All four compounds were validated to cause hypocholesterolemia in Neuro-2a cells. The morpholine-like fungicides, fenpropimorph and spiroxamine, mirrored their Neuro-2a activity in four immortalized human cell lines and in a human neuroprogenitor model derived from hiPSCs, but endosulfan sulfate and tributyltin chloride did not. CONCLUSIONS: These data reveal the existence of environmental compounds that interrupt cholesterol biosynthesis and that methodologically hiPSC neuroprogenitor cells provide a particularly sensitive system to monitor the effect of small molecules on de novo cholesterol formation.