Estudo do mecanismo e mediadores químicos envolvidos na atividade pró-inflamatória das lectinas de sementes de Vatairea macrocarpa e Dioclea violacea

Abstract

The lectins are proteins that possess at least a carbohydrate-binding site. For this reason, they are capable of interacting with cells and exhibit a variety of biological activities. In previous studies, it was demonstrated that the antiinflammatory activity of some plant lectins is probably due to a competitive blockade of a common leukocyte and/or endothelial selectin carbohydrate ligand. Thus we have investigated possible pro-inflammatory activity of lectins from seeds of Dioclea violacea (DvL; MW 100,2 kDa; glucose-mannose-binding) and Vatairea macrocarpa (Vmac; MW 100 kDa; galactose-binding) upon neutrophil migration (NM), in vivo and in vitro, as well as the role of resident peritoneal cells and the underlying mechanisms. The following models were used in vivo: peritonitis, paw edema and air pouch. Neutrophil chemotactic gradient, cultured macrophages and

splenocytes were used in vitro. It was verified that the two lectins exhibit pro- inflammatory activity in all the in vivo models. The depletion of resident cells through

the washing of the peritoneal cavity reduced the NM induced by two lectins. The increase of macrophages by treatment with thioglycollate potentiated the NM by Vmac but it had not effect on that induced by DvL. On the other hand, the mast cell depletion by treatment with compound 48/80 had no effect on NM induced by DvL or Vmca. This suggests macrophage involvement and discards it of mast cells. In the pharmacological modulation using antiinflammatory drugs, it was observed that dexamethasone (DEXA) and thalidomide, but not indomethacin, MK-886 and BN50730, inhibited NM induced by DvL and Vmac in the peritonitis model. The two lectins did not induce neutrophil chemotaxis in vitro , however, when Vmac was incubated with macrophages it induced the release of a neutrophil chemotactic substance (MW > 5 kDa). This substance had its activity inhibited by DEXA and antibodies against TNF-a, suggesting the involvement of this cytokine in this effect. Cultured splenocytes with DvL release a neutrophil chemotactic substance (MW > 5 kDa) which was inhibited by DEXA and antibodies against TNF-a and IL-1 , suggesting a possible participation of these two cytokines in NM induced by DvL. The paw edema induced by DvL and Vmac was inhibited in leucopenic animals. The suggestion of leucocyte involvement in this effect is corroborated by the histopathological analysis of rat paws which showed cell infiltration. Methylmannoside and D-galactose inhibited the NM induced by DvL and Vmac, respectively. It seems that although DvL and Vmac induce NM by different mechanisms, the inflammatory response is mediated by interaction of their lectin domains with sugars on the macrophage membranes. For this interaction to result in an inflammatory response the maintenance of the three dimentional structures of the two lectins is necessary as well as the specific metal-binding sites present in DvL.