Pseudomonas aeruginosa controls production of its multiple virulence factors and biofilm development via the quorum sensing (QS) system. QS signals also interact with and affect the behavior of eukaryotic cells. Host water homeostasis and aquaporins (AQP) are essential during pathological conditions since they interfere with the cell cytoskeleton and signaling, and hereby affect cell morphology and functions. We investigated the contribution of F? aeruginosa QS genes lasl/rhIl to phagocytosis, cell morphology, AQP9 expression, and distribution in human macrophages, using immunoblotting, confocal, and nanoscale imaging. Wild type F? aeruginosa with a functional QS system was a more attractive prey for macrophages than the lasl/rhIl mutant lacking the production of QS molecules, 30-C-12-HSL, and C-4 -HSL, and associated virulence factors. The F? aeruginosa infections resulted in elevated AQP9 expression and relocalization to the leading and trailing regions in macrophages, increased cell area and length; bacteria with a functional QS system lasl/rhIl achieved stronger responses. We present evidence for a new role of water fluxes via AQP9 during bacteria macrophage interaction and for the QS system as an important stimulus in this process. These novel events in the interplay between F? aeruginosa and macrophages may influence on the outcome of infection, inflammation, and development of disease.

Quorum sensing (QS) communication allows Pseudomonas aeruginosa to collectively control its population density and the production of biofilms and virulence factors. QS signal molecules, like N-3-oxo-dodecanoyl-L-homoserine lactone (30-C-12-HSL), can also affect the behavior of host cells, e.g., by modulating the chemotaxis, migration, and phagocytosis of human leukocytes. Moreover, host water homeostasis and water channels aquaporins (AQP) are critical for cell morphology and functions as AQP interact indirectly with the cell cytoskeleton and signaling cascades. Here, we investigated how P aeruginosa 30-C-12-HSL affects cell morphology, area, volume and AQP9 expression and distribution in human primary macrophages, using quantitative PCR, immunoblotting, two- and three-dimensional live imaging, confocal and nanoscale imaging. Thus, 30-C-12-HSL enhanced cell volume and area and induced cell shape and protrusion fluctuations in macrophages, processes tentatively driven by fluxes of water across cell membrane through AQP9, the predominant AQP in macrophages. Moreover, 30-C-12-HSL upregulated the expression of AQP9 at both the protein and mRNA levels. This was accompanied with enhanced whole cell AQP9 fluorescent intensity and redistribution of AQP9 to the leading and trailing regions, in parallel with increased cell area in the macrophages. Finally, nanoscopy imaging provided details on AQP9 dynamics and architecture within the lamellipodial area of 30-C-12-HSL-stimulated cells. We suggest that these novel events in the interaction between P aeruginosa and macrophage may have an impact on the effectiveness of innate immune cells to fight bacteria, and thereby resolve the early stages of infections and inflammations.

Crimean–Congo hemorrhagic fever virus (CCHFV) is an arthropod-borne pathogen that causes infectious disease with severe hemorrhagic manifestations in vascular system in humans. The proper function of the cells in the vascular system is critically regulated by aquaporins (AQP), water channels that facilitate fluxes of water and small solutes across membranes. With Hazara virus as a model for CCHFV, we investigated the effects of viruses on AQP6 and the impact of AQP6 on virus infectivity in host cells, using transiently expressed GFP-AQP6 cells, immunofluorescent assay for virus detection, epifluorescent imaging of living cells and confocal microscopy. In GFP-AQP6 expressing cells, Hazara virus reduced both the cellular and perinuclear AQP6 distribution and changed the cell area. Infection of human cell with CCHFV strain IbAR 10200 downregulated AQP6 expression at mRNA level. Interestingly, the overexpression of AQP6 in host cells decreased the infectivity of Hazara virus, speaking for a protective role of AQP6. We suggest the possibility for AQP6 being a novel player in the virus–host interactions, which may lead to less severe outcomes of an infection.