Age-related differences in the neutrophil response to pulmonary pseudomonas infection

• Published in: Experimental gerontology 2014-06, Vol.54, p.42-46
• Main Authors: Chen, Michael M., Palmer, Jessica L., Plackett, Timothy P., Deburghgraeve, Cory R., Kovacs, Elizabeth J.
• Format: Article
• Language: English
• Subjects: Age Factors; Aging; Analysis of Variance; Animals; Chemokine CXCL1 - metabolism; Female; Immune System Diseases - physiopathology; Infection; Inflamm-aging; Inflammation; Leukocyte Disorders - physiopathology; Mice, Inbred BALB C; Neutrophil; Neutrophils - immunology; Pneumonia; Pneumonia, Bacterial - immunology; Pseudomonas aeruginosa; Pseudomonas aeruginosa - immunology; Pseudomonas Infections - immunology; Pseudomonas Infections - physiopathology; Survival Analysis
• ISSN: 0531-5565; 1873-6815
• DOI: 10.1016/j.exger.2013.12.010

Pseudomonas aeruginosa pneumonia is more common and more lethal in the elderly. The immunologic underpinnings of this increased incidence and mortality have not been evaluated, however are assumed to be a complication of age-associated immune dysfunction. Young (10–12week old) and aged (18–20month old) BALB/c mice were subjected to intratracheal infection of P. aeruginosa. Animals were sacrificed 24h after inoculation. The lungs were collected for analysis of lung pathology, chemokine levels, neutrophil counts, and myeloperoxidase activity. Pulmonary levels of the neutrophil chemokine KC are significantly higher in aged mice relative to young following P. aeruginosa infection. Despite this, neutrophil counts are higher in young mice compared to aged mice after infection. Furthermore, the neutrophils are predominantly found in the air space of young infected mice. This correlated with increased myeloperoxidase activity from bronchoalveolar lavage specimens of young mice relative to aged mice after infection. Neutrophil migration into the lungs is impaired in aged mice 24h after intratracheal infection despite elevated chemokine levels, suggesting that immunosenescence is impairing neutrophil migration. •Aged mice exhibit greater mortality than young mice after pulmonary bacterial infection.•Despite an increased leukocytosis and pulmonary KC levels, aged mice accumulate less pulmonary neutrophils after infection.•The abated neutrophil response was accompanied by an apparent inability of neutrophils to extravasate into the air space.•Aging impairs directed neutrophil migration which may contribute to the susceptibility of the elderly to bacterial pneumonia.