Pro-inflammatory effect of Arum maculatum lectin and role of resident cells

Arum maculatum agglutinin (AMA) is a monocot lectin isolated from tubers of Arum maculatum L. (Araceae) which exhibits different specificity towards oligo-mannosidic-type and N-acetyllactosaminic-type glycans. We have investigated the effect of this lectin on the cells of the immune system. Models of neutrophil migration in vivo, neutrophil chemotaxis in vitro and macrophage cultures were used to study the lectin inflammatory activity. When administered into rat peritoneal cavities, AMA (80, 200 and 500 microg/mL/cavity) induced significant and dose-dependent neutrophil migration. This effect was inhibited by incubation with alpha-methyl-d-mannoside. A 83% depletion in the number of resident cells following peritoneal lavage did not reduce the AMA-induced neutrophil migration, as compared to sham animals (not washed). However, pre-treatment with 3% thioglycolate which increases the peritoneal macrophage population by 236%, enhanced the neutrophil migration induced by AMA (200 microg/mL/cavity) (119%, p < 0.05). Reduction of peritoneal mast cell population by chronic treatment of cavities with compound 48/80 did not modify AMA-induced neutrophil migration. The neutrophil chemotaxy assay in vitro shows that the lectin (300 microg/mL) induces neutrophil chemotaxy (368% p < 0.05) compared to RPMI. Finally, injection into peritoneal cavities of supernatants from macrophage cultures obtained after stimulation with AMA (300 microg/mL) enhanced neutrophil migration (110% p < 0.05). Summarizing, our data suggest that A. maculatum agglutinin presents pro-inflammatory activity, inducing neutrophil migration by two ways, one which is independent on resident cells and another one dependent on the presence of these cells.