title: PECAM-1 dampens cytokine levels during LPS-induced endotoxemia by regulating leukocyte trafficking.
abstract: OBJECTIVE
  To investigate the mechanism by which platelet endothelial cell adhesion molecule 1 (PECAM-1/CD31), an immunoglobulin (Ig)-superfamily cell adhesion and signaling receptor, regulates pro-inflammatory cytokine levels. The purpose of the present investigation was to test the hypothesis that PECAM-1 influences circulating cytokine levels by regulating the trafficking of activated, cytokine-producing leukocytes to sites of inflammation.
  
  
  METHODS
  PECAM-1+/+ and PECAM-1-/- mice were subjected to lipopolysaccharide (LPS)-induced endotoxemia, and systemic cytokine levels were measured by Bioplex multiplex cytokine assays. Flow cytometry was employed to enumerate leukocytes at inflammatory sites and to measure cytokine synthesis in leukocyte sub-populations. Enzyme-linked immunosorbent assay (ELISA) was used to measure cytokine levels in tissue samples and in supernatants of in vitro-stimulated leukocytes.
  
  
  RESULTS
  We confirmed earlier reports that mice deficient in PECAM-1 had greater systemic levels of pro-inflammatory cytokines following intraperitoneal (IP) LPS administration. Interestingly, expression of PECAM-1, in mice, had negligible effects on the level of cytokine synthesis by leukocytes stimulated in vitro with LPS and in peritoneal macrophages isolated from LPS-injected mice. There was, however, excessive accumulation of macrophages and neutrophils in the lungs of PECAM-1-deficient, compared with wild-type, mice--an event that correlated with a prolonged increase in lung pro-inflammatory cytokine levels.
  
  
  CONCLUSIONS
  Our results demonstrate that PECAM-1 normally functions to dampen systemic cytokine levels during LPS-induced endotoxemia by diminishing the accumulation of cytokine-producing leukocytes at sites of inflammation, rather than by modulating cytokine synthesis by leukocytes.
authors: Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI 53201, United States.
authors: Jamie R
authors: JR
authors: Privratsky
authors: Sarah B
authors: SB
authors: Tilkens
authors: Debra K
authors: DK
authors: Newman
authors: Peter J
authors: PJ
authors: Newman
mesh_terms: D000818:Animals; D002448:Cell Adhesion / Q000276:immunology; D002465:Cell Movement / Q000276:immunology; D018932:Chemokine CCL2 / Q000097:blood; D004198:Disease Susceptibility; D019446:Endotoxemia / Q000139:chemically induced* / Q000276:immunology / Q000378:metabolism; D005434:Flow Cytometry; D007249:Inflammation / Q000276:immunology / Q000503:physiopathology; D007274:Injections, Intraperitoneal; D015850:Interleukin-6 / Q000097:blood / Q000378:metabolism; D007962:Leukocytes / Q000276:immunology / Q000378:metabolism; D008070:Lipopolysaccharides / Q000008:administration & dosage* / Q000009:adverse effects; D008168:Lung / Q000276:immunology / Q000378:metabolism; D008264:Macrophages / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009504:Neutrophils / Q000276:immunology / Q000378:metabolism; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000032:analysis / Q000378:metabolism*
chemical_list: C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D015850:Interleukin-6; D008070:Lipopolysaccharides; D019408:Platelet Endothelial Cell Adhesion Molecule-1