Effect of metabolic inhibitors on the agglutination of tumor cells by concanavalin A and Ricinus communis agglutinin

Antimicrobial, anti-inflammatory and anti-arthritic activity of hemolymph lectin (NagLec) isolated from the freshwater crab, Oziotelphusanaga

Lectins are non-immune glycoproteins or proteins having a unique capacity to interact with carbohydrate ligands found on the surface of their host cells. In the present investigation, the lectin was purified from the hemolymph of freshwater crab, Oziotelphusa naga and its antimicrobial, anti-inflammatory and anti-arthritic activity was analysed. The preliminary characterization of the hemagglutinin was carried out to identify the erythrocyte and sugar specificity, optimum pH and temperature and cation dependency. The agglutinin was found to be highly specific to rabbit erythrocyte and inhibited by fetuin and α-lactose. Maximum hemagglutination activity was noted at pH 7.5-8 and temperature 20-40 °C. An O-acetyl sialic acid specific 75 kDa hemolymph lectin, designated as NagLec was isolated from the freshwater crab, Oziotelphusa naga by affinity chromatography on fetuin coupled Sepharose 4 B, with a purification fold of 185. The bacteria Staphylococcus aureus, Proteus mirabilis and fungus Candida albicans had the greatest zone of inhibition when treated with NagLec. The results of the Minimum inhibitory concentration (MIC) and Minimum bactericidal concentration (MBC) assays showed that the purified lectin inhibited the growth of Staphylococcus aureus at 0.031 and 0.065 μg/ml, which proved the bactericidal property of NagLec. NagLec generated alterations on the bacterial cells and led to protein leakage, which was dosage (24 and 48 μg/ml) and time dependent (10-40 min). COX and LOX enzyme was inhibited to 49.43% and 61.81% with 100 μg/ml concentration of NagLec respectively, demonstrating NagLec's ability to reduce inflammation. Furthermore, NagLec (500 μg) suppressed protein denaturation up to 77.12% whereas diclofenac sodium (a standard drug) was inhibited by 89.36%. The results indicate that NagLec, a sialic acid specific lectin isolated from the freshwater crab O. naga could be formulated as a nano drug in future owing to its antimicrobial, anti-inflammatory and anti-arthritic potential that could be targeted to specific pathogenic microbes and treat arthritis.

Structure and stability of Ricinus communis haemagglutinin

The molecular properties of the haemagglutinin of Ricinus communis (RCA I or RCA 120) were evaluated by analytical ultracentrifugation, light-scattering, c.d. and fluorescence. The native molecule had a fairly expanded structure (f/f0 = 1.43) and dissociated into two subunits of equal size in 6 M-guanidinium chloride. This native structure was stable in alkali (up to pH 11) and resistant to thermal denaturation at neutrality. A pH-triggered change in the haemagglutinin conformation was observed and characterized by analytical ultracentrifugation, c.d. and fluorescence between pH 7 and 4.5, the range in which its affinity for galactosides decreased [Yamasaki, Absar & Funatsu (1985) Biochim, Biophys. Acta 828, 155-161]. These results are discussed in relation to those reported in the literature for other lectins and more especially ricin, for which a pH-dependent conformation transition has been observed in the same range of low pH.

Effects of glutaraldehyde and other drugs on concanavalin A-mediated red blood cell adsorption to nonsenescent, senescent and transformed human fibroblasts

Concanavalin A (Con A)-mediated red blood cell (RBC) adsorption with the RBC coating method (in which Con A-coated RBC's are adsorbed to fibroblasts) was greatly increased by glutaraldehyde fixation of RBCs before Con A-coating and decreased by the fixation of fibroblasts. On the other hand, RBC adsorption with the fibroblast coating method (in which RBCs are adsorbed to Con A-coated fibroblasts) was decreased by the fixation of RBCs and increased by the fixation of fibroblasts before Con A coating. The fixation of RBCs or fibroblasts after Con A coating did not have these effects. In addition, the fixation of both RBCs and fibroblasts nearly completely abolished RBC adsorption with either method. However, the amount of [3H] Con A binding was not affected by the fixation. RBC adsorption with the fibroblast coating method was also affected by cytochalasin B, colchicine, NaN3 and dibucane treatments of fibroblasts. These drug treatments of fibroblasts, however, did not affect RBC adsorption with the RBC coating method, except cytochalasin B. In addition, the effects of drug treatments of fibroblasts examined occurred nearly to the same extent for nonsenescent, senescent, and transformed cells. Our results suggest that secondary processes after Con A binding, receptor mobility and receptor association with cytoskeletals, play important roles in RBC adsorption, but that the roles do not change with aging or transformation.

Lectin-mediated agglutination of murine lymphoma cells. Cell surface deformability and reversibility of agglutination by saccharides

Agglutination of S49 mouse lymphoma cells by Ricinus communis I agglutinin can be reversed by the competing haptenic saccharide, lactose, soon after agglutination, but after further incubation in the absence of lectin the agglutination reaction could not be reversed by lactose and the cells remained as multicell aggregates. The irreversibility of S49 cell agglutination was time, temperature and lectin concentration dependent and its onset correlated with ultrastructurally observed deformation of adjacent cell surfaces and an increase in the proportion of adjacent cell surface areas in close apposition within multicell aggregates. Pretreatment of S49 cells with cytochalasin B or cytochalasin B plus vinblastine enhanced R. communis I agglutinin-mediated agglutination, while vinblastine alone and fluoride plus azide had essentially no effect. When drug-treated cells were agglutinated and then incubated in lectin-free drug-containing media for various times prior to lactose addition, the drug effects were more pronounced. Cytochalasin B alone or with vinblastine inhibited lactose reversal of S49 cell agglutination compared to the drug-free controls, while fluoride plus azide enhanced hapten reversibility. Electron microscopic analysis revealed that the onset of agglutination irreversibility correlated with cell surface deformation in the drug-treated cells. Cell aggregates that were more readily reversible by lactose (fluoride plus azide) were unchanged or less deformed, while S49 aggregates treated with cytochalasin B plus vinblastine were more deformed compared to controls without drugs. These experiments suggest a role for cell surface deformability as an important secondary effect during lectin-mediated cell agglutination of S49 lymphoma cells.

Concanavalin A as a quantitative and ultrastructural probe for normal and neoplastic cell surfaces

Concanavalin A (Con A) has been popularly used as a cell surface probe for normal and neoplastic cells. Differences between normal fibroblasts and their transformed derivatives were examined using Con A agglutination, quantitative labeling with 125I-Con A and ultrastructural labeling with fluorescent- or ferritin-Con A. Con A agglutinates confluent-SV3T3 and 3T3 cells at midpoints of 20-60 and greater than, 500-2,000 mug/ml, respectively, and sparse cells at 5-15 and 1,200-1,500 mg/ml, respectively. Quantitative binding of 125I-Con A at 4 degrees C (10 or 15 min) with saturating lectin concentrations does not indicate a difference in the number of Con A receptors on sparse or confluent 3T3 and SV3T3 cells similar to many publications, but contrary to Noonan and Burger (1973). Under these conditions of labeling, ferritin-Con A is not internalized, indicating absence of endocytosis. The lateral mobility of Con A receptors and their relative ability to be aggregated on the cell surface by Con A was investigated with fluorescent- and ferritin-Con A. The initial distribution of Con A receptors on 3T3, SV3T3 and MSV3T3 cells under conditions of labeling at low temperature (0-5 degrees C) or to fixed cells was essentially randomly dispersed, but changes quickly to aggregated on SV3T3 and MSV3T3 (but not 3T3) after shifting the temperature to 20-37 degrees C, indicating, in general, a greater relative mobility of Con A receptors on SV3T3 and MSV3T3 cells. The aggregated Con A receptors seem to be directly involved in cell agglutination because they are usually found at the sites of cell-to-cell contact during 10 min agglutination experiments with ferritin-Con A. When confluent-3T3 cells are labeled on monolayer with ferritin-Con A at 0-4 degrees C, washed and then shifted to 20-37 degrees C for 10-15 min prior to in situ embedding, two classes of Con A receptors can be identified. One class appears to have low relative mobility and is associated with the 3T3 cell's extensive subplasma membrane microfilament network, while the other is capable of being aggregated and eventually endocytosed. On confluent-SV3T3 cells, only the latter class of receptors appears to be present, indicating a possible loss of cytoplasmic control over the distribution and mobility of lectin-binding sites on transformed cell surfaces.

Effects of concanavalin A on the isolated perfused rat liver

In the isolated perfused liver, Concanavalin A provoked a significant decrease of flow rate within 2 to 4 min. which was dose-dependent and could be partly inhibited by specific antagonists. Furthermore it was found that the lectin led to a decline of the respiration, an increase of the lactate/pyruvate ratio and a release of the transaminases into the medium. It was suggested that Concanavalin A displaced endothelial cells in the liver capillaries, which occluded the vessels and decreased the flow rate. The decreased respiration was considered to be secondary to this effect.