title: Platelet-leucocyte aggregates form in the mesenteric vasculature in patients with ulcerative colitis.
abstract: OBJECTIVE
  Inflammation and thrombosis are closely related processes, which may play a role in the pathogenesis, as well as complications, of inflammatory bowel disease (IBD). Platelet activation and platelet-leucocyte aggregation are increased and platelet aggregation is known to occur in the mesenteric vasculature in IBD. The aims of this study were to test the hypotheses that platelet-leucocyte aggregation, platelet activation and neutrophil activation occur in the mesenteric vessels of patients with ulcerative colitis (UC).
  
  
  METHODS
  Platelet-leucocyte aggregates (PLAs), platelet activation (P-selectin expression) and neutrophil activation (L-selectin expression, which decreases on neutrophil activation) were assessed flow cytometrically in mesenteric arterial, and venous blood sampled in eight patients with UC and eight controls with colonic carcinoma undergoing intestinal resections.
  
  
  RESULTS
  In the patients with UC, the number of PLAs in the mesenteric vein exceeded that in the artery, the median rise being 38% (P=0.02). In UC, arterial PLA numbers were 0.17 (0.02-0.32) (median, range) x 10(9)/l versus venous 0.26 (0.09-1.6) x 10(9)/l (P=0.02). The median percentage increase was 45%. Mesenteric PLA formation did not occur in patients with colonic carcinoma [arterial 0.06 (0.03-0.49) x 10(9)/l vs. venous 0.05 (0.02-0.35) x 10(9)/l; P=0.55]. The median percentage change was +45% for UC patients and -5% for controls. No arteriovenous gradient was observed in P-selectin expression, but L-selectin expression (arbitrary units), increased in the mesenteric vasculature of the UC patients [arterial 839 (503-995), venous 879 (477-1035); P=0.03] and fell in those with colonic carcinoma [arterial 900 (660-959), venous 850 (546-957); P=0.04]. The median percentage change was +4% for UC and -7% for controls.
  
  
  CONCLUSIONS
  The finding of increased numbers of PLAs in the venous mesenteric circulation supports the hypothesis that activated vascular endothelium stimulates PLA formation in UC.
authors.affiliation: Centre for Gastroenterology, Queen Mary School of Medicine, Barts and the London NHS Trust, London, UK.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Irving
authors.forename: Marion G
authors.initials: MG
authors.lastname: Macey
authors.forename: Roger M
authors.initials: RM
authors.lastname: Feakins
authors.forename: Charles H
authors.initials: CH
authors.lastname: Knowles
authors.forename: John N
authors.initials: JN
authors.lastname: Frye
authors.forename: Sidath H
authors.initials: SH
authors.lastname: Liyanage
authors.forename: Sina
authors.initials: S
authors.lastname: Dorudi
authors.forename: Norman S
authors.initials: NS
authors.lastname: Williams
authors.forename: David S
authors.initials: DS
authors.lastname: Rampton
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002449:Cell Aggregation; D003093:Colitis, Ulcerative / Q000097:blood*; D004730:Endothelium, Vascular / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D006801:Humans; D007962:Leukocytes / Q000502:physiology*; D008297:Male; D008642:Mesenteric Veins / Q000378:metabolism; D008875:Middle Aged; D018375:Neutrophil Activation; D019007:P-Selectin / Q000378:metabolism*; D010974:Platelet Aggregation; D016896:Treatment Outcome
chemical_list: D019007:P-Selectin