Triflamp, a snake venom metalloproteinase, reduces neutrophil-platelet adhesion through proteolysis of PSGL-1 but not glycoprotein Ib alpha.

Triflamp, a metalloproteinase isolated from Trimeresurus flavo-viridis, inhibits heterotypic adhesion between platelets and neutrophils. Coincubation studies demonstrate that direct interaction of triflamp with neutrophils is sufficient to inhibit the formation of neutrophil-platelet complexes. Its anti-adhesive effect is in a concentration- and incubation time-dependent manner. Triflamp reduces the expression of P-selectin glycoprotein ligand-1 (PSGL-1) on neutrophils and glycoprotein (GP) Ibalpha on platelets as probed by flow cytometry and Western blot. Moreover, triflamp disrupts P-selectin-mediated adhesion by cleaving PSGL-1 from the neutrophil surface. There are obvious differences regarding PSGL-1 proteolysis by triflamp and cathepsin G. Besides the NH2-terminus of PSGL-1, other sites are truncated by triflamp. The inhibitory effect of triflamp on PSGL-1 expression was prevented by pretreatment with a metalloproteinase inhibitor, phenanthroline. However, triflamp-treated platelets fully keep the ability for binding to PAF- or fMLP-stimulated neutrophils. Our results indicate that degradation of platelet GPIb alpha by triflamp does not interfere with neutrophil-platelet adhesion. Its effect on neutrophil PSGL-1 appears to be a critical factor for its inhibition on neutrophil-platelet interaction.