Lectin of Pisum arvense seeds induces in-vivo and in-vitro neutrophil migration

PAL is a glucose/mannose-specific lectin isolated from Pisum arvense seeds. Previously, we demonstrated the capacity of other leguminous lectins to induce oedema formation and neutrophil stimulation. To investigate the potential pro-inflammatory activity of PAL, we have studied its ability to induce neutrophil migration into peritoneal cavities of rats and neutrophil chemotaxis in-vitro. The role of resident cells and sugar residues on PAL activity was analysed. PAL or saline (control) were administered intraperitoneally to rats, and total and differential leucocyte (macrophages, neutrophils and mast cells) counts were performed. The role of resident cells on the PAL effect was evaluated using three strategies: reducing the total resident cell population by lavage of rat cavities with saline; increasing macrophage population by treating animals with thioglycolate; and depleting mast cell population by subchronic treatment of rats with compound 48/80. PAL induced in-vitro and in-vivo neutrophil migration. In-vivo, PAL (50, 100, 200 and 300 mu g) significantly (P < 0.05) and dose-dependently increased neutrophil migration by 600, 740, 900 and 940%, respectively, showing maximal effect 4h after injection. PAL induced mononuclear cell migration. The neutrophil stimulatory effect of PAL was potentiated in animals treated with both thioglycolate and compound 48/80. The indirect lectin chemotactic effect was shown in rats injected with supernatant from cultured macrophages stimulated by PAL. In conclusion, PAL was shown to exhibit in-vivo and in-vitro pro-inflammatory activity. The in-vivo effect seemed to occur by a dual mechanism that was independent, but also dependent, on resident cells.