title: Evaluation of four α-diketones for toll-like receptor-4 (TLR-4) activation in a human transfected cell line.
abstract: Toll-like receptor-4 (TLR-4) activity is upregulated in persons with fibrotic lung diseases secondary to chronic inflammatory conditions like Crohn's disease and rheumatoid arthritis. We hypothesized that α-diketones associated with fixed obstructive lung disease may activate TLR-4. We utilized a human embryonic kidney cell assay (HEK293) with human TLR-4 receptors to test for potential activation effects of 2,3-butandeione, 2,3-pentanedione, 2,3-hexanedione, and 2,3-heptanedione at test concentrations of 1, 10, 100, and 1000 µM. The assay detects NF-κB-induced expression of secreted alkaline phosphatase measured after 16 h incubation by a UV-VIS Spectrometer at 650 nm. Escherichia coli K12 lipopolysaccharide (LPS) at 0.5 ng/mL served as a positive control and was added with each test compound to evaluate combined effects. None of the tested α-diketones were found to exhibit cytotoxicity, agonism, or synergistic effects with LPS in the human TLR-4 assay up to 1000 µM. Screening of 2,3-butanedione for agonist activity using the HEK assay with mouse TLR-4 receptors exhibited cytotoxicity at 1000 µM, but no agonist activity. We conclude that the tested α-diketones at relatively high concentrations in vitro do not exhibit TLR-4 agonist or synergistic activity and, therefore, apparently do not directly induce inflammasome activation through this pathway in humans or mice.
authors.affiliation: Cardno ChemRisk, 130 Vantis, Suite 170, Aliso Viejo, CA 92656, USA. Electronic address: brent.kerger@cardno.com.
authors.forename: Brent D
authors.initials: BD
authors.lastname: Kerger
authors.affiliation: Cardno ChemRisk, 101 2nd St. Suite 700, San Francisco, CA 94105, USA.
authors.forename: Kerry A
authors.initials: KA
authors.lastname: Thuett
authors.affiliation: Cardno ChemRisk, 231 Front St. Suite 201, Brooklyn, NY 11201, USA.
authors.forename: Brent L
authors.initials: BL
authors.lastname: Finley
mesh_terms: D003931:Diacetyl / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D057809:HEK293 Cells / Q000187:drug effects; D006588:Hexanones / Q000494:pharmacology*; D006801:Humans; D007659:Ketones / Q000494:pharmacology*; D010422:Pentanones / Q000494:pharmacology*; D051197:Toll-Like Receptor 4 / Q000037:antagonists & inhibitors / Q000187:drug effects*; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D006588:Hexanones; D007659:Ketones; D010422:Pentanones; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; C043231:2,3-hexanedione; D003931:Diacetyl; C013186:2,3-pentanedione
keywords: Bronchiolitis obliterans; Diacetyl; Fibrotic lung disease; Humans; Inflammasome