title: Involvement of intracellular Ca2+ dynamics in cytoprotective action by amino acids and cytotoxicity by sodium laurate, an absorption enhancer.
abstract: In our previous studies, taurine (Tau) and L-glutamine protected intestinal epithelial cells from local toxicity caused by sodium laurate (C12), an absorption enhancer, while maintaining sufficient absorption-enhancing effect of C12, and it was suggested that one of the mechanisms behind cytoprotection by amino acids was to prevent intracellular Ca2+ concentration ([Ca2+]i) from increasing. In the present study, we focused on the elucidation of mechanisms by which C12 increases [Ca2+]i and by which amino acids suppress [Ca2+]i by utilizing Caco-2 cells. Removal of extracellular Ca2+ remarkably suppressed the increase of [Ca2+]i by C12. Compound 48/80, an inhibitor of phospholipase C, and verapamil, a Ca2+ channel inhibitor, also significantly prevented [Ca2+]i elevation. These results indicate that C12 augmented [Ca2+]i due to (a) influx of extracellular Ca2+ through Ca2+ channel, (b) release of Ca2+ from the endoplasmic reticulum. Cytoprotective action by amino acids was significantly attenuated by orthovanadate, an inhibitor of plasma membrane Ca2+-ATPase (PMCA), suggesting that amino acids activate PMCA to enhance the efflux of intracellular Ca2+. Furthermore, Tau enhanced the mitochondrial uptake of Ca2+, which could contribute to the decrease in [Ca2+]i. These results clearly show that amino acids protect intestinal epithelial cells from being damaged by modulating intracellular Ca2+ dynamics.
authors.affiliation: Department of Pharmaceutics, Faculty of Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima-naka, Okayama 700-8530, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Okuda
authors.forename: Kenta
authors.initials: K
authors.lastname: Kadotsuji
authors.forename: Chie
authors.initials: C
authors.lastname: Takayama
authors.forename: Kiyonori
authors.initials: K
authors.lastname: Hanada
authors.forename: Fuyuki
authors.initials: F
authors.lastname: Mukaizawa
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Ogawara
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Higaki
authors.forename: Toshikiro
authors.initials: T
authors.lastname: Kimura
mesh_terms: D001120:Arginine / Q000494:pharmacology*; D018938:Caco-2 Cells; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D005973:Glutamine / Q000494:pharmacology*; D006706:Homeostasis / Q000187:drug effects; D006801:Humans; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism; D007850:Lauric Acids / Q000494:pharmacology*; D013654:Taurine / Q000494:pharmacology*; D014700:Verapamil / Q000494:pharmacology; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D002614:Chelating Agents; D007850:Lauric Acids; D005973:Glutamine; C030358:lauric acid; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D013654:Taurine; D003189:p-Methoxy-N-methylphenethylamine; D004533:Egtazic Acid; D001120:Arginine; D014700:Verapamil; D002118:Calcium