Inhibition of gap junction communication in alveolar epithelial cells by 18alpha-glycyrrhetinic acid.
Cultured alveolar epithelial cells exhibit gap junction intercellular communication (GJIC) and express regulated levels of connexin (Cx) 43 mRNA and protein. Newly synthesized radiolabeled Cx43 protein equilibrates with phosphorylated Cx43 isoforms; these species assemble to form both connexons and functional gap junction plaques. The saponin 18alpha-glycyrrhetinic acid (GA) rapidly and reversibly blocks GJIC at low concentrations (5 microM). Extended exposure to 18alpha-GA at higher concentrations causes inhibition of GJIC and time- and dose-dependent reductions in both Cx43 protein and mRNA expression. The latter toxic effects are paralleled by disassembly of gap junction plaques and are reversed less readily than acute effects on GJIC. These observations demonstrate 18alpha-GA-sensitive regulation of intercellular communication in epithelial cells from the mammalian lung and suggest a role for Cx43 expression and phosphorylation in acute and chronic regulation of GJIC between alveolar epithelial cells.
Guo
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Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA.
Martinez-Williams
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Gilbert
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Rannels
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D000818:Animals; D002417:Cattle / Q000097:blood / Q000196:embryology; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects / Q000502:physiology; D005312:Fetal Blood / Q000502:physiology; D017629:Gap Junctions / Q000187:drug effects / Q000473:pathology / Q000502:physiology*; D006034:Glycyrrhetinic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D010766:Phosphorylation; D020033:Protein Isoforms / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D012333:RNA, Messenger / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D014018:Tissue Distribution / Q000502:physiology
D018031:Connexin 43; D020033:Protein Isoforms; D012333:RNA, Messenger; C119129:18alpha-glycyrrhetinic acid; D006034:Glycyrrhetinic Acid