Rat paw edema and leukocyte immigration induced by plant lectins

Lectins from Dioclea grandiflora (DG) and Canavalia brasiliensis (CB) were compared with Concanavalin A (ConA) for their ability to induce paw edema and peritoneal cell immigration in rats. ConA caused a slight edema with a peak at 1 h after injection, while DG or CB induced a pronounced and long-lasting edema that reached a maximum at about 6 h. Different antiinflammatory drugs partially inhibited the edema. alpha-D-glucose (GLU) partially blocked the edema caused by ConA and markedly inhibited that due to CB, but had no effect on the edema induced by DG. alpha-Methyl mannoside (alpha-MM) blocked the edema caused by DG and ConA, but did not affect that caused by CB. At doses much lower than those used to induce paw edema, the lectins promoted an intense accumulation of neutrophil and mononuclear cells in the rat peritoneal cavity. CB and DG were more potent than ConA, which also presented a different profile of cell immigration. GLU significantly inhibited leukocyte accumulation caused by all lectins. alpha-MM impaired ConA- and DG-induced cell immigration, but only partially inhibited CB. Thus, despite their physicochemical similarities with ConA, DG and CB have more powerful pro-inflammatory effects. This difference seems to be related to their sugar-binding properties. However, while ConA- and DG-induced effects were inhibited more by alpha-MM than by GLU, CB-induced effects were inhibited more by glucose.