Human neutrophil-derived CAP37 inhibits lipopolysaccharide-induced activation in murine peritoneal macrophages.
Human cationic antimicrobial protein, CAP37, is released from neutrophil granules during infection. CAP37 attracts monocytes, binds Gram-negative endotoxin (lipopolysaccharide, LPS), is bactericidal for a range of Gram-negative bacteria, and reduces mortality in murine polymicrobial sepsis. Here, we report that recombinant CAP37 specifically targets murine peritoneal macrophages. Under steady-state conditions, the bulk of cell-associated CAP37 was localized at the plasma membrane. However, a fraction of CAP37 gained access to the endocytic system, but did not accumulate in recycling endosomes or in the trans-Golgi network (TGN). Instead, CAP37 was internalized by fluid phase endocytosis and accumulated in a prelysosomal compartment. Macrophages that were preexposed to CAP37 exhibited diminished LPS responsiveness, as determined by analysis of c-Jun phosphorylation. Further examination showed that pretreatment with CAP37 reduced the ability of macrophages to bind LPS. Taken together, these observations demonstrate that prolonged exposure to CAP37 desensitizes macrophages to LPS and suggest that this protein plays a novel anti-inflammatory role in polymicrobial sepsis.
Department of Surgery, Zurich University Hospital, Sternwartstrasse 14, CH-8091 Zurich, Switzerland. herbert.bosshart@usz.ch
Herbert
H
Bosshart
Michael
M
Heinzelmann
D000818:Animals; D023181:Antimicrobial Cationic Peptides; D015415:Biomarkers; D001798:Blood Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008070:Lipopolysaccharides / Q000276:immunology / Q000378:metabolism*; D017737:Macrophages, Peritoneal / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D010766:Phosphorylation
C062991:AZU1 protein, human; D023181:Antimicrobial Cationic Peptides; D015415:Biomarkers; D001798:Blood Proteins; D002352:Carrier Proteins; D008070:Lipopolysaccharides; D048031:JNK Mitogen-Activated Protein Kinases