title: Structure-activity relationship of capsaicin analogs and transient receptor potential vanilloid 1-mediated human lung epithelial cell toxicity.
abstract: Activation of intracellular transient receptor potential vanilloid-1 (TRPV1) in human lung cells causes endoplasmic reticulum (ER) stress, increased expression of proapoptotic GADD153 (growth arrest- and DNA damage-inducible transcript 3), and cytotoxicity. However, in cells with low TRPV1 expression, cell death is not inhibited by TRPV1 antagonists, despite preventing GADD153 induction. In this study, chemical variants of the capsaicin analog nonivamide were synthesized and used to probe the relationship between TRPV1 receptor binding, ER calcium release, GADD153 expression, and cell death in TRPV1-overexpressing BEAS-2B, normal BEAS-2B, and primary normal human bronchial epithelial lung cells. Modification of the 3-methoxy-4-hydroxybenzylamide vanilloid ring pharmacophore of nonivamide reduced the potency of the analogs and rendered several analogs mildly inhibitory. Correlation analysis of analog-induced calcium flux, GADD153 induction, and cytotoxicity revealed a direct relationship for all three endpoints in all three lung cell types for nonivamide and N-(3,4-dihydroxybenzyl)nonanamide. However, the N-(3,4-dihydroxybenzyl)nonanamide analog also produced cytotoxicity through redox cycling/reactive oxygen species formation, shown by inhibition of cell death by N-acetylcysteine. Molecular modeling of binding interactions between the analogs and TRPV1 agreed with data for reduced potency of the analogs, and only nonivamide was predicted to form a "productive" ligand-receptor complex. This study provides vital information on the molecular interactions of capsaicinoids with TRPV1 and substantiates TRPV1-mediated ER stress as a conserved mechanism of lung cell death by prototypical TRPV1 agonists.
authors.affiliation: Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, UT 84112, USA.
authors.forename: Karen C
authors.initials: KC
authors.lastname: Thomas
authors.forename: Manivannan
authors.initials: M
authors.lastname: Ethirajan
authors.forename: Kiumars
authors.initials: K
authors.lastname: Shahrokh
authors.forename: Hao
authors.initials: H
authors.lastname: Sun
authors.forename: Jeewoo
authors.initials: J
authors.lastname: Lee
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Cheatham
authors.forename: Garold S
authors.initials: GS
authors.lastname: Yost
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Reilly
mesh_terms: D002118:Calcium / Q000378:metabolism; D002211:Capsaicin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000187:drug effects*; D005470:Fluorometry; D006801:Humans; D008168:Lung / Q000166:cytology / Q000187:drug effects*; D008958:Models, Molecular; D012313:RNA / Q000096:biosynthesis / Q000235:genetics; D020545:Respiratory Mucosa / Q000166:cytology / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013329:Structure-Activity Relationship; D050916:TRPV Cation Channels / Q000187:drug effects*; D051742:Transcription Factor CHOP / Q000096:biosynthesis / Q000235:genetics
chemical_list: C497249:DDIT3 protein, human; D050916:TRPV Cation Channels; C494482:TRPV1 protein, human; D051742:Transcription Factor CHOP; D012313:RNA; D002211:Capsaicin; D002118:Calcium