title: Endothelium down-regulates Fas, TNF, and TRAIL-induced neutrophil apoptosis.
abstract: BACKGROUND
  Neutrophil (PMN) apoptosis regulates PMN functional longevity and is integral to the resolution of inflammation. We have recently shown that PMN contact with an endothelial monolayer down-regulates spontaneous PMN apoptosis. We sought to explore endothelial-mediated down-regulation of PMN apoptosis following mediator-induced apoptosis. We tested the three known membrane-initiated, receptor-ligand apoptotic pathways: Fas, tumor necrosis factor-alpha (TNF), and TNF-related apoptosis inducing ligand (TRAIL).
  
  
  METHODS
  PMNs were isolated from peripheral venous blood of healthy volunteers. PMNs were co-cultured in the absence and presence of a human coronary artery endothelial cell (HCAEC) monolayer for 4 h. PMNs were then stimulated with the pro-apoptotic agonists (agonistic anti-Fas IgM, TNF, and TRAIL) for one hour, followed by an assessment of apoptosis after 5 h. PMN apoptosis was measured using an acridine orange/ethidium bromide in situ fluorescent microscopy assay. Caspase 3 activity was assessed using a spectrophotometric assay.
  
  
  RESULTS
  In addition to spontaneous PMN apoptosis, endothelial co-culture resulted in significant increases in the percentages of normal cells and decreased percentages of apoptotic cells after stimulation with agonistic anti-Fas IgM, TNF and TRAIL. Endothelial co-culture did not alter PMN caspase 3 activity.
  
  
  CONCLUSIONS
  Endothelial-mediated down-regulation of PMN apoptosis is conferred after 4 h of co-culture. In addition to spontaneous apoptosis, endothelial contact down-regulated the three known membrane-initiated PMN apoptotic pathways: Fas, TNF, and TRAIL. These data imply that endothelial-mediated down-regulation of PMN apoptosis may involve defects in each apoptotic pathway or a single defect in a distal transduction or effector event common to all three pathways. Alterations in the activity of caspase 3 did not appear to serve as a mechanism for endothelial-mediated down-regulation of PMN apoptosis.
authors.affiliation: Department of Surgery, John D. Dingell Veterans Affairs Medical Center, Wayne State University School of Medicine, Detroit, Michigan 48201, USA. steven.tennenberg@med.va.gov
authors.forename: Steven D
authors.initials: SD
authors.lastname: Tennenberg
authors.forename: Raphaela
authors.initials: R
authors.lastname: Finkenauer
authors.forename: Tao
authors.initials: T
authors.lastname: Wang
mesh_terms: D000328:Adult; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D053148:Caspase 3; D020169:Caspases / Q000187:drug effects / Q000502:physiology; D015536:Down-Regulation / Q000187:drug effects* / Q000502:physiology*; D004727:Endothelium / Q000187:drug effects* / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D007249:Inflammation / Q000503:physiopathology*; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D009504:Neutrophils / Q000187:drug effects* / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013530:Surgical Wound Infection / Q000503:physiopathology*; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D019014:fas Receptor / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; D008562:Membrane Glycoproteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D019014:fas Receptor; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases