Abstract
Pseudomonas aeruginosa is the predominant respiratory tract pathogen in patients with cystic fibrosis (CF), and its resistance to phagocytosis may contribute to its virulence. P. aeruginosa ingestion by macrophages occurs only in the presence of D-glucose or D-mannose, sugars present in low concentrations in the endobronchial space. Here we show that only isolates of P. aeruginosa and not other bacterial species were ingested by murine macrophages in a glucose-dependent manner. Glucose transport inhibitors blocked both [3H]-2-deoxy-glucose (2dG) uptake and phagocytosis of P. aeruginosa. P. aeruginosa pretreated with 2dG or 5-thio-D-glucose (5TG) was efficiently ingested. Macrophages pretreated with 2dG or 5TG were able to bind but unable to ingest P. aeruginosa in the presence of glucose; however, they efficiently ingested zymosan or IgG-coated sheep erythrocytes. Macrophages produced lactate only from glucose or mannose. The facilitative glucose transporter GLUT1 mRNA transcript was detected by PCR in preparations from purified macrophages. The nucleotide sequence of the PCR product was identical to that published for murine GLUT1. GLUT1 protein was detected with anti-GLUT1-peptide polyclonal Abs. We conclude that glucose exerts its effect on the macrophage, not on the bacterium, in the glucose-dependent nonopsonic phagocytosis of P. aeruginosa and that glucose transport via GLUT1 by the macrophages is required to trigger ingestion. The unique glucose dependency for phagocytosis of P. aeruginosa by macrophages may contribute to the pathogenicity of this bacterial species in CF patients.
