Characterization of thrombin-induced leukocyte rolling and adherence: a potential proinflammatory role for proteinase-activated receptor-4.
It is commonly accepted that thrombin exerts its proinflammatory properties through the activation of proteinase-activated receptor (PAR)-1, although two other thrombin receptors have been discovered: PAR-3 and PAR-4. In this study, we have investigated the mechanisms and the receptors involved in thrombin-induced leukocyte/endothelial cell interactions by using selective agonists and antagonists of thrombin receptors in an in vivo intravital microscopy system. Topical addition of selective PAR-1 agonists to rat mesenteric venules failed to reproduce the increased leukocyte rolling and adhesion observed after thrombin topical addition. When added together with the selective PAR-1 antagonist RWJ-56110, thrombin was still able to provoke increased leukocyte rolling and adherence. The thrombin-induced leukocyte rolling and adherence was not affected by pretreatment of rats with an anti-platelet serum. Selective PAR-4-activating peptide was able to reproduce the effects of thrombin on leukocyte rolling and adhesion. Intraperitoneal injection of PAR-4-activating peptide also caused a significant increase in leukocyte migration into the peritoneal cavity. In rat tissues, PAR-4 expression was detected both on endothelium and isolated leukocytes. Taken together, these results showed that in rat mesenteric venules, thrombin exerts proinflammatory properties inducing leukocyte rolling and adherence, by a mechanism independent of PAR-1 activation or platelet activation. However, PAR-4 activation either on endothelial cells or on leukocytes might be responsible for the thrombin-induced effects. These findings suggest that PAR-4 activation could contribute to several early events in the inflammatory reaction, including leukocyte rolling, adherence and recruitment, and that in addition to PAR-1, PAR-4 could be involved in proinflammatory properties of thrombin.
Mucosal Inflammation Research Group, Department of Pharmacology and Therapeutics, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada. nvergnol@ucalgary.ca
Nathalie
N
Vergnolle
Claudia K
CK
Derian
Michael R
MR
D'Andrea
Martin
M
Steinhoff
Patricia
P
Andrade-Gordon
D000818:Animals; D002465:Cell Movement / Q000187:drug effects; D004730:Endothelium, Vascular / Q000737:chemistry; D007962:Leukocytes / Q000187:drug effects* / Q000502:physiology; D008297:Male; D015539:Platelet Activation; D051381:Rats; D017208:Rats, Wistar; D044463:Receptor, PAR-1; D018179:Receptors, Thrombin / Q000502:physiology*; D013917:Thrombin / Q000494:pharmacology*
D044463:Receptor, PAR-1; D018179:Receptors, Thrombin; D013917:Thrombin; C112908:protease-activated receptor 4