Ambroxol stimulates the activity of goblet cells, thereby reducing the viscosity of bronchial mucus. It also stimulates the production of surfactant in type II pneumocytes, and in consequence, the mucus formed does adhere less to bronchial walls. Both mechanisms facilitate coughing up. Furthermore, in vitro studies suggest antibacterial and antiviral properties of ambroxol: it reduced both, the number of pathogens and the formation of inflammatory mediators in infections with rhinoviruses in primary human tracheal epithelial cells [3] and suppressed the multiplication of the influenza virus in a mouse model [4]. In addition, ambroxol has anti-inflammatory properties, by modulating various cytokines. Ambroxol also has a local anaesthetic effect via inhibition of sodium channels.
BelgiëNew scientific findings on the mucokinetic effect of ambroxol
Known mechanisms of action of ambroxol
Importance of mucociliary clearance
Novel insights into ambroxol-induced and calcium-mediated signalling in murine ciliated lung airway epithelial cells
A prior investigation highlighted that ambroxol enhances the movement and bending amplitude of cilia in cells by raising the level of calcium within the cells [5]. This increase is achieved by facilitating the release of calcium from internal cell storage and, more importantly, through the entry of calcium into the cell via specific calcium channels (CaV1.2). The following research by Nakahari and colleagues [2] has further elucidated that the observed enhancements in ciliary activity are primarily governed by two cellular signalling mechanisms: one related to the cellular pH level, and the other one to the concentration of chloride ions within the cell. Initially, ambroxol triggers the specific calcium channels in ciliated lung epithelial cells, leading to a rise in cellular calcium. This surge in calcium activates a transporter mechanism that imports bicarbonate (HCO3–) into the cell, thereby elevating the cell’s internal pH and, consequently, boosting ciliary beat frequency and amplitude. Additionally, the increase in calcium levels stimulates a protein (anoctamine 1 or ANO1) that speeds up the release of chloride ions from the cilia, reducing the internal concentration of chloride ions. Detailed analysis of these mechanisms showed that the pH-related pathway contributes to a significant increase in both ciliary beat frequency (by 30%) and amplitude (by 15–20%), whereas the chloride ion pathway also enhances amplitude (by 10–15%) but does not noticeably affect ciliary beat frequency.
Fig. 1. Schematic diagram of the ambroxol-stimulated mucokinetic effect.
Ambroxol (ABX) stimulates the Ca2+ entry via CaV1.2 and increases internal calcium levels. In turn, calcium increase stimulates NBC to accelerate bicarbonate (HCO3−) entry. The HCO3− entering via NBC binds H+ to increase internal pH. The Ca2+ entry directly stimulates ANO1 in cilia to activate Cl− secretion, which decreases internal chloride levels. The internal pH increase enhances the CBF and CBA; while internal [Cl–] decrease enhances the CBA [modified according to 2].
Clinical translation: Recommendation of ambroxol for acute cough
Literature
- Kardos P, et al. Guidelines of the German Respiratory Society for diagnosis and treatment of adults suffering from acute, subacute and chronic cough. Pneumologie 2019;73:143–80.
- Nakahari T, et al. Ambroxol-enhanced frequency and amplitude of beating cilia controlled by a voltage-gated Ca2+ channel, CaV1.2, via pHi increase and [Cl−]i decrease in the lung airway epithelial cells of mice. Int J Mol Sci 2023;24:16976. doi: 10.3390/ijms242316976.
- Yamaya M, et al. Ambroxol inhibits rhinovirus infection in primary cultures of human tracheal epithelial cells. Arch Pharm Res 2014;37(4):520–529. doi: 10.1007/s12272-013-0210-7.
- Yang B, et al. Ambroxol suppresses Influenza-virus proliferation in the mouse airway by increasing antiviral factor levels. Eur Respir J 2002;19(5):952-958). doi: 10.1183/09031936.02.00253302.
- Saito D, et al. Ambroxol-enhanced ciliary beating via voltage-gated Ca2+ channels in mouse airway ciliated cells. Eur J Pharmacol 2023;941:175496. doi:10.1016/j.ejphar.2023.175496.
Conflicts of interest: Conflict of interest: M. Brodowska, H. Graeter and P. Fontanilla are employees of Sanofi. During manuscript preparation L. Noah was a Sanofi employee.
Disclosure: Medical writing and publication funded by Sanofi.
