Pharmacological analysis of the neutrophil migration induced by D. rostrata lectin: involvement of cytokines and nitric oxide.

In the present study, we investigated the involvement of resident cell and inflammatory mediators in the neutrophil migration induced by chemotactic activity of a glucose/mannose-specific lectin isolated from Dioclea rostrata seeds (DrosL). Rats were injected i.p. with DrosL (125-1000 microg/cavity), and at 2-96 h thereafter the leukocyte counts in peritoneal fluid were determined. DrosL-induced a dose-dependent neutrophil migration accumulation, which reached maximal response at 24 h after injection and declines thereafter. The carbohydrate ligand nearly abolished the neutrophil influx. Pre-treatment of peritoneal cavities with thioglycolate which increases peritoneal macrophage numbers, enhanced neutrophil migration induced by DrosL by 303%. However, the reduction of peritoneal mast cell numbers by treatment of the cavities with compound 48/80 did not modify DrosL-induced neutrophil migration. The injection into peritoneal cavities of supernatants from macrophage cultures stimulated with DrosL (125, 250 and 500 microg/ml) induced neutrophil migration. In addition, DrosL treatment induced cytokines (TNF-alpha, IL-1beta and CINC-1) and NO release into the peritoneal cavity of rats. Finally, neutrophil chemotaxis assay in vitro showed that the lectin (15 and 31 microg/ml) induced neutrophil chemotaxis by even 180%. In conclusion, neutrophil migration induced by D. rostrata lectin occurs by way of the release of NO and cytokines such as IL-1beta, TNF-alpha and CINC-1.

Vatairea macrocarpa (Leguminosae) lectin activates cultured macrophages to release chemotactic mediators.

The lectin from the legume Vatairea macrocarpa is a galactose/N-acetylgalactosamine binding protein that induced cellular inflammatory response mediated by resident cells. This study investigated which inflammatory mediators would be released from lectin-activated cells. The intraperitoneal injection in rats of the supernatant from cultured macrophages, but not from mast cells, stimulated with lectin induced a time- and dose-dependent release of a neutrophil chemotactic factor, termed MNCF-VML. Pharmacological modulation with dexamethasone inhibited both the lectin-induced chemotactic activity in vivo and also the lectin-induced release of MNCF-VML into the supernatant of cultured macrophages. Cyclooxygenase and lipoxygenase metabolites are apparently not involved in the action of this factor or its release, since indomethacin or MK886 were unable to affect the lectin response. The molecular weight of MNCF-VML was found to be greater than 5 kDa, which led to the investigation of which cytokine(s) could be involved by the following approaches: (a) treatment of animals with antiserum to tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-1, or IL-8 before intraperitoneal injection of lectin and (b) addition of antiserum to TNF-alpha, IL-1, or IL-8 to the supernatant of lectin-stimulated macrophages before intraperitoneal administration. Antiserum to TNF-alpha, but not IL-1 nor IL-8, inhibited the neutrophil migration induced either by lectin or MNCF-VML. Our data suggest that neutrophil migration induced by V. macrocarpa lectin occurs via the release of cytokines such as TNF-alpha by macrophages. Thus, this lectin may represent an important tool to better understand pathological situations where an excess of leukocytes at inflammatory sites causes tissue injury.