Anti-inflammatory effect of glucose-mannose binding lectins isolated from Brazilian beans

Selectins are essential for leukocyte recruitment in inflammation. Because of a lectin domain present in the selectin structure, we investigated the anti-inflammtory activity of six mannose-glucose binding lectins from brazilian beans: Dioclea guianensis-DguiL; D. grandiflora-DgL; Cratylia floribunda-CfL; D. violacea-D.vL; D. virgata-DvirL and Canavalia brasiliensis-ConBr. The lectins were injected intravenously (i.v.) into rats (0.1 and 1.0 mg/kg; 30 min before irritants) and its activities compared to E. coli endotoxin (LPS, 30 mu g/kg i,v,), Three lectins DvL, CfL and DguiL), although less intense than LPS, inhibited the neutrophil migration induced by carrageenan (Cg, 300 mu g) in a dose-dependent manner (0,1 and 1.0 mg/kg), DvL activity was reversed by 0,1 M alpha-D-methyl-mannoside (alpha-CH3), but not by 0,1 M alpha-D-galactose, The fMLP (44 ng)-induced neutrophil migration was also reduced by these lectins, Endotoxin contamination of lectin samples could be excluded since alpha-CH3 treatment reversed the DvL effect, but did not modify LPS inhibitory activity, Carrageenan (300 mu g)-induced paw oedema was also reduced by LPS or lectin treatments, Conversely, none of the tested lectins inhibited dextran (Dex, 300 mu g)-induced paw oedema, a classical leukocyte independent model, or zymosan (Zy, 1,0 mg)-induced peritonitis and paw oedema. LPS showed no effect upon Dex-induced paw oedema and barely reduced (25%) the oedematogenic effects of zymosan, As proposed for LPS, the lectin inhibitory activity was better observed on neutrophil-mediated inflammatory reactions, We speculate that the plant lectin antiinflammatory activity is probably due to a competitive blockage of a common leukocyte and/or endothelial selectin carbohydrate Ligand.