title: Neutrophil depletion inhibits early and late monocyte/macrophage increase in lung inflammation.
abstract: Monocytes/macrophages have critical impact on outcomes of lung inflammation. Kinetics and mechanisms for the increase of monocytes/macrophages in lungs are not completely understood. To better understand these mechanisms, E. coli-LPS (250 micro grams; N = 35) or endotoxin-free saline (N = 5) were instilled intratracheally in Sprague-Dawley rats and the increase in monocytes/macrophages, neutrophils and monocyte chemotactic protein-1 (MCP-1) was quantified at various time points after LPS treatment. In contrast to typical pattern of neutrophil influx between 6 and 24 hours, monocytes/macrophages increased in two distinct phases, very early at 3 hours and late at 24 hours. The role of neutrophils in monocyte/macrophage increase was addressed in LPS-challenged neutropenic rats (N = 8). Neutrophil depletion before instillation of LPS abrogated the early as well as late monocyte/macrophage increases in the lung. Quantification of MCP-1, which is one of the major chemoattractants for monocytes, in lung homogenates showed similar concentrations in neutropenic and non-neutropenic LPS-challenged rats. These findings show that increase in monocytes/macrophages in lung occurs in two, early and late phases, both being dependent on neutrophils but not on MCP-1.
authors.affiliation: Immunology Research Group, Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada.
authors.forename: Kyathanahalli S
authors.initials: KS
authors.lastname: Janardhan
authors.forename: Simran K
authors.initials: SK
authors.lastname: Sandhu
authors.forename: Baljit
authors.initials: B
authors.lastname: Singh
mesh_terms: D000818:Animals; D018932:Chemokine CCL2 / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D007150:Immunohistochemistry; D007249:Inflammation / Q000378:metabolism*; D007700:Kinetics; D008070:Lipopolysaccharides / Q000378:metabolism; D008168:Lung / Q000378:metabolism / Q000473:pathology*; D008264:Macrophages / Q000166:cytology* / Q000378:metabolism; D008297:Male; D008854:Microscopy, Electron; D016253:Microscopy, Immunoelectron; D015233:Models, Statistical; D009000:Monocytes / Q000166:cytology* / Q000378:metabolism; D009503:Neutropenia; D009504:Neutrophils / Q000378:metabolism*; D011014:Pneumonia; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D018932:Chemokine CCL2; D008070:Lipopolysaccharides