title: Identification of Environmental Quaternary Ammonium Compounds as Direct Inhibitors of Cholesterol Biosynthesis.
abstract: In this study, we aim to identify environmental molecules that can inhibit cholesterol biosynthesis, potentially leading to the same biochemical defects as observed in cholesterol biosynthesis disorders, which are often characterized by congenital malformations and developmental delay. Using the Distributed Structure-Searchable Toxicity (DSSTox) Database Network developed by EPA, we first carried out in silico screening of environmental molecules that display structures similar to AY9944, a known potent inhibitor of 3β-hydroxysterol-Δ(7)-reductase (DHCR7)-the last step of cholesterol biosynthesis. Molecules that display high similarity to AY9944 were subjected to test in mouse and human neuroblastoma cells for their effectiveness in inhibiting cholesterol biosynthesis by analyzing cholesterol and its precursor using gas chromatography-mass spectrometry. We found that a common disinfectant mixture, benzalkonium chlorides (BACs), exhibits high potency in inhibiting DHCR7, as suggested by greatly elevated levels of the cholesterol precursor, 7-dehydrocholesterol (7-DHC). Subsequent structure-activity studies suggested that the potency of BACs as Dhcr7 inhibitors decrease with the length of their hydrocarbon chain: C10 > C12 ≫ C14 > C16. Real-time qPCR analysis revealed upregulation of the genes related to cholesterol biosynthesis and downregulation of the genes related to cholesterol efflux, suggesting a feedback response to the inhibition. Furthermore, an oxidative metabolite of 7-DHC that was previously identified as a biomarker in vivo was also found in cells exposed to BACs by liquid chromatography-mass spectrometry. Our findings suggest that certain environmental molecules could potently inhibit cholesterol biosynthesis, which could be a new link between environment and developmental disorders.
authors.affiliation: *Department of Medicinal Chemistry, University of Washington, Seattle, Washington; Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, Washington;
authors.forename: Josi
authors.initials: J
authors.lastname: Herron
authors.affiliation: Department of Chemistry, Vanderbilt University, Nashville, Tennessee.
authors.forename: Rosalyn C
authors.initials: RC
authors.lastname: Reese
authors.affiliation: Department of Chemistry, Vanderbilt University, Nashville, Tennessee.
authors.forename: Keri A
authors.initials: KA
authors.lastname: Tallman
authors.affiliation: Department of Chemistry, Vanderbilt University, Nashville, Tennessee.
authors.forename: Rohini
authors.initials: R
authors.lastname: Narayanaswamy
authors.affiliation: Department of Chemistry, Vanderbilt University, Nashville, Tennessee.
authors.forename: Ned A
authors.initials: NA
authors.lastname: Porter
authors.affiliation: *Department of Medicinal Chemistry, University of Washington, Seattle, Washington; libinxu@uw.edu.
authors.forename: Libin
authors.initials: L
authors.lastname: Xu
mesh_terms: D000818:Animals; D000891:Anti-Infective Agents, Local / Q000737:chemistry / Q000633:toxicity*; D001548:Benzalkonium Compounds / Q000737:chemistry / Q000633:toxicity*; D045744:Cell Line, Tumor; D002784:Cholesterol / Q000096:biosynthesis*; D016208:Databases, Factual; D004305:Dose-Response Relationship, Drug; D004785:Environmental Pollutants / Q000737:chemistry / Q000633:toxicity*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D050356:Lipid Metabolism / Q000187:drug effects*; D051379:Mice; D015394:Molecular Structure; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000037:antagonists & inhibitors / Q000378:metabolism; D018570:Risk Assessment; D013329:Structure-Activity Relationship; D001371:trans-1,4-Bis(2-chlorobenzaminomethyl)cyclohexane Dihydrochloride / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000891:Anti-Infective Agents, Local; D001548:Benzalkonium Compounds; D004785:Environmental Pollutants; D004791:Enzyme Inhibitors; D001371:trans-1,4-Bis(2-chlorobenzaminomethyl)cyclohexane Dihydrochloride; D002784:Cholesterol; D044925:Oxidoreductases Acting on CH-CH Group Donors; C019995:7-dehydrocholesterol reductase
keywords: 7-dehydrocholesterol; DHCR7; benzalkonium chlorides; cholesterol biosynthesis inhibition; quaternary ammonium compounds.