Joint Processing of Apoptotic Cells and Pseudomonas aeruginosa by Macrophages

ADRIANA JAGER; PAULA ARIAS; MARIA VICTORIA PEPE; VIRGINIA TRIBULATTI; ARLINET KIERBEL

Paraná

Congreso; LIV Reunión de la Sociedad Argentina de Biquímica y Biología Molecular; 2018

Pseudomonas aeruginosa (PA) is an opportunistic pathogen that infects vulnerable patients such as those with cystic fibrosis (CF). CF is characterized by an increased number of apoptotic cells in the airways as well as impaired efferocytosis: a process in which apoptotic cells are engulf and dispose of by other cells. We have shown that PA binds to apoptotic cells and is internalized by epithelial cells through efferocytosis. Bacteria are then eliminated intracellularly. Here we demonstrate that bacteria-laden apoptotic cells are targets for J774 macrophage-like cells and Bone Marrow-Derived Macrophages (BMM). Macrophages internalize apoptotic cells and PA individually or together, constituting three differentiated cell populations: macrophages with apoptotic cells, with PA, and with both. Classically or alternatively activated macrophages display enhanced phagocytic or efferocytic programs, respectively. Our aim is to evaluate the response elicited by macrophages facing both stimuli (i.e. bacteria and apoptotic cells) simultaneously. To study bacterial clearance we measured intracellular survival over time. Both types of macrophage cells eliminate PA, which was found inside LAMP1-positive vesicles suggesting that its final fate is elimination inside lysosomes. Also apoptotic material was found inside these vesicles. We also analyzed the phagocytic and efferocytic efficiency. The presence of PA diminishes apoptotic cell uptake. However, the presence of apoptotic cells does not affect the uptake/elimination of bacteria, suggesting that macrophages displayed rather a phagocytic phenotype non-withstanding the presence of apoptotic cells.