Expression of COX-2 in platelet-monocyte interactions occurs via combinatorial regulation involving adhesion and cytokine signaling
J. Clin. Invest. Dan A. Dixon, et al. 116:2727 doi:10.1172/JCI27209 [Go to this article.]

Figure 1
Activated platelets induce COX-2 expression in monocytes. (A) Activation of platelets (plts) is required for COX-2 mRNA (left panel) and protein (right panel) expression. Monocytes (10⁶ cells) were incubated with control M199 medium (co), thrombin (IIa), inactivated platelets (10⁸ cells), or thrombin-activated platelets. After 18 hours, COX-2 mRNA was detected by RNase protection assays. GAPDH mRNA is shown as a control for RNA loading. COX-2 protein was detected by immunoblot of 50 μg of total cell lysate. β-actin was detected on the same blot as a control for protein loading. Data shown represent 3 experiments. (B) Immunofluorescent detection of COX-2 and P-selectin in thrombin-activated platelet-monocyte aggregates. Freshly isolated platelets were incubated with monocytes for 18 hours and examined by immunocytochemical analysis. Immunofluorescent staining for COX-2 is shown in red (top right); immunofluorescent staining for P-selectin, a platelet marker, is shown in green (top left). Merged immunofluorescence and phase contrast images are shown (bottom left and right). (C) COX activity in monocytes (mono) and monocyte/platelet suspensions (mono+plts) treated with medium (co) or thrombin (IIa) for 18 hours. COX-2 inhibition was accomplished by pretreating cells for 1 hour with 10 μM NS-398 (NS). PGE₂ levels were measured by ELISA in the medium containing arachidonic acid and indicate the average of duplicate experiments.