Extracellular Adenosine Protects against Streptococcus pneumoniae Lung Infection by Regulating Pulmonary Neutrophil Recruitment

PLoS Pathogens

Stacie Clark¹  Elsa N. Bou Ghanem¹  John M. Leong¹  Philip G. Haydon²  Sally R. McIver²  Sara E. Roggensack³  Pilar Alcaide⁴ 

[1] Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America;Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts, United States of America;Program in Molecular Microbiology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, Massachusetts, United States of America;Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine and Molecular Cardiology Research Institute, Tufts Medical Center, Boston, Massachusetts, United States of America

关键词: Pneumococcus;    Adenosine;    Blood;    Respiratory infections;    Inflammation;    Bacteremia;    Signal inhibition;    Inflammatory diseases;   

DOI  :  10.1371/journal.ppat.1005126

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

An important determinant of disease following Streptococcus pneumoniae (pneumococcus) lung infection is pulmonary inflammation mediated by polymorphonuclear leukocytes (PMNs). We found that upon intratracheal challenge of mice, recruitment of PMNs into the lungs within the first 3 hours coincided with decreased pulmonary pneumococci, whereas large numbers of pulmonary PMNs beyond 12 hours correlated with a greater bacterial burden. Indeed, mice that survived infection largely resolved inflammation by 72 hours, and PMN depletion at peak infiltration, i.e. 18 hours post-infection, lowered bacterial numbers and enhanced survival. We investigated host signaling pathways that influence both pneumococcus clearance and pulmonary inflammation. Pharmacologic inhibition and/or genetic ablation of enzymes that generate extracellular adenosine (EAD) (e.g. the ectoenzyme CD73) or degrade EAD (e.g. adenosine deaminase) revealed that EAD dramatically increases murine resistance to S. pneumoniae lung infection. Moreover, adenosine diminished PMN movement across endothelial monolayers in vitro, and although inhibition or deficiency of CD73 had no discernible impact on PMN recruitment within the first 6 hours after intratracheal inoculation of mice, these measures enhanced PMN numbers in the pulmonary interstitium after 18 hours of infection, culminating in dramatically elevated numbers of pulmonary PMNs at three days post-infection. When assessed at this time point, CD73-/- mice displayed increased levels of cellular factors that promote leukocyte migration, such as CXCL2 chemokine in the murine lung, as well as CXCR2 and β-2 integrin on the surface of pulmonary PMNs. The enhanced pneumococcal susceptibility of CD73-/- mice was significantly reversed by PMN depletion following infection, suggesting that EAD-mediated resistance is largely mediated by its effects on PMNs. Finally, CD73-inhibition diminished the ability of PMNs to kill pneumococci in vitro, suggesting that EAD alters both the recruitment and bacteriocidal function of PMNs. The EAD-pathway may provide a therapeutic target for regulating potentially harmful inflammatory host responses during Gram-positive bacterial pneumonia.

【 授权许可】

CC BY