A new role for an old drug: Ambroxol triggers lysosomal exocytosis via pH-dependent Ca2+ release from acidic Ca2+ stores. Issue 6 (December 2015)

• Record Type: Journal Article
• Authors: Fois, Giorgio; Hobi, Nina; Felder, Edward; Ziegler, Andreas; Miklavc, Pika; Walther, Paul; Radermacher, Peter; Haller, Thomas; Dietl, Paul
• Is Part Of: Cell calcium. Volume 58:Issue 6(2015)
• Page Start: 628
• Page End: 637
• Publication Date: 2015-12
• Subjects: Ax Ambroxol -- Baf A1 bafilomycin A1 -- BCECF (2′, 7′-Bis-(2-Carboxyethyl)-5-(and-6)-Carboxyfluorescein -- [Ca2+]c cytoplasmic Ca2+ concentration -- ER endoplasmic reticulum -- EDX energy-dispersive X-ray spectroscopy -- exc excitation -- em emission -- GPN glycyl-l-phenylalanine-beta-naphthylamide -- IP3 Inositol-1, 4, 5-trisphosphat -- LB lamellar body -- LEL late endosome lysosome -- LRO lysosome-related organelle -- LSYB LysoSensor Yellow/Blue -- LTG LysoTracker Green; Secretory lysosome -- Autophagy -- Neurodegeneration -- Lysosomal storage disease -- Mucus -- Parkinson's disease -- Alzheimer's disease -- Inflammation -- Host defense; Calcium -- Metabolism -- Periodicals; Vertebrates -- Physiology -- Periodicals; Calcium -- Physiological effect -- Periodicals; Cell physiology -- Periodicals; Calcium in the body -- Periodicals; 572.516
• DOI: 10.1016/j.ceca.2015.10.002
• Languages: English
• ISSNs: 0143-4160

Abstract

Graphical abstract: Highlights: Type II pneumocytes containing lamellar bodies, secretory lysosomes, were studied. Ambroxol accumulates in lamellar bodies and disintegrates their ultrastructure. Ambroxol neutralizes the lamellar body pH. pH neutralization by Ambroxol or NH3 /NH4 + releases Ca 2+ from acidic stores. Ambroxol stimulates Ca 2+ -dependent exocytosis of lamellar bodies. Abstract: Ambroxol (Ax) is a frequently prescribed drug used to facilitate mucociliary clearance, but its mode of action is yet poorly understood. Here we show by X-ray spectroscopy that Ax accumulates in lamellar bodies (LBs), the surfactant storing, secretory lysosomes of type II pneumocytes. Using lyso- and acidotropic substances in combination with fluorescence imaging we confirm that these vesicles belong to the class of acidic Ca 2+ stores. Ax lead to a significant neutralization of LB pH, followed by intracellular Ca 2+ release, and to a dose-dependent surfactant exocytosis. Ax-induced Ca 2+ release was significantly reduced and slowed down by pretreatment of the cells with bafilomycin A1 (Baf A1), an inhibitor of the vesicular H + ATPase. These results could be nearly reproduced with NH3 /NH4 + . The findings suggest that Ax accumulates within LBs and severely affects their H + and Ca 2+ homeostasis. This is further supported by an Ax-induced change of nanostructural assembly of surfactant layers. We conclude that Ax profoundly affects LBs presumably by disordering lipid bilayers and by acting as a weak base. The pH change triggers – at least in part – Ca 2+ release from stores and secretion of surfactant from type II cells. This novel mechanism of Ax as a lysosomal secretagogue may also play a role for its recently discussed use for lysosomal storage and other degenerative diseases.