Based on the work of Ghani & Soothill [15] and Sriramulu et al. [16], we utilized 0.5% mucin (1X) in our ASM+. But more recently, Henke et al. [36], showed that the concentrations of MUC5AC and MUC5B, the principal gel-forming mucins, are decreased in airway

secretions from CF patients with stable disease and greatly increased during pulmonary exacerbations (by 89% and 908%, respectively). When we reduced the mucin concentration of ASM+ by 50% (0.5X), the gelatinous mass still formed in the well, possibly through the contribution of other ASM+ components (DNA and lecithin) that add to the viscosity. However, the typical multilayered BLS was eliminated and replaced with a structure that appears Angiogenesis inhibitor to consist of small microcolonies amid individual cells and tiny cell clusters distributed throughout most of the gelatinous mass (Figure 4A, B). Surprisingly, the effect of increasing the concentration of mucin to 2X on the development of BLS was similar to that induced by reducing the mucin concentration. Rather than the distinct highly structured BLS architecture, PAO1 produced small microcolonies distributed throughout the ASM+ (Figure 4C). At this time, we do not know if the increase in the availability of mucin glycoprotein interferes with the development of microcolonies that coalesce to form the well-developed BLS. One of the hallmarks of the CF syndrome Dabrafenib mouse is the

overproduction of mucin within the lung alveoli [1, 3, 7]. Yet during P. aeruginosa infection of the CF lung alveoli, the level of mucin may vary [36].

P. aeruginosa LPS induces the production of reactive oxygen intermediates, which cause release of transforming growth factor α; TGF-α then up-regulates the expression of MUC-5 AC thereby causing excessive mucin production [37–39]. However, P. aeruginosa Selleckchem BMS345541 produces other factors that may reduce the amount of mucus within its immediate vicinity; alveolar mucin is degraded by P. aeruginosa extracellular serine proteases such as LasB [40]. Ultimately, the interaction of all these factors would produce a net mucin concentration suitable for the full development of the BLS, while any imbalance in the production of ADAMTS5 these factors that reduces or increases mucin concentration would prevent the establishment of the BLS. Alternatively, BLS may form in the initial stages of P. aeruginosa infection in the CF lung. Treatment that reduces the amount of mucin present would disperse the bacteria making them more susceptible to antibacterial treatment (stable disease). Alternatively, mucin may reduce the chances of forming new BLS. Extracellular DNA is another contributor to the viscosity of CF sputum [15, 16]. Within the CF lung, there are several sources for this extracellular DNA – dead host immune cells, lysed bacteria, QS-regulated release of P. aeruginosa DNA, and outer membrane vesicles that contain DNA [41, 42].