Concanavalin A-induced inhibition of abrin and ricin activity parallels with a decrease of the number of toxin-binding uptake-elution cycles

Bleomycin Loaded Magnetic Chitosan Nanoparticles as Multifunctional Nanocarriers

Iron oxide (Fe3O4) containing magnetic chitosan nanoparticles were prepared with Concanavalin-A and Bleomycin as multifunctional nanocarriers for the targeted cancer therapy by co-precipitation techniques. The chemical structures of nanoparticles were analyzed by FTIR and the magnetic properties of the nanoparticles were evaluated by electron spin resonance technique and vibrational scanning mangnetometer measurements. The in vitro release profiles of Bleomycin were investigated and chitosan nanoparticles characteristics were optimized for subsequent in vivo applications. The magnetic chitosan nanoparticles are biocompatible-based MTT assays. The therapeutic potential of these nanoparticles are being investigated for in vivo applications.

Effect of gangliosides on binding, internalization and cytotoxic activity of ricin

The only gangliosides in Burkitt's lymphoma EB-3 cells is GM3. Treatment of Burkitt's lymphoma EB-3 cells with gangliosides GM1 or GM3 results in their binding to and partial incorporation into the cell membrane. About 25% of cell-associated ganglioside GM1 can interact with the ricin. However, such an increase in the number of binding sites does not enhance but rather decreases the cytotoxic effect of ricin. A similar protective effect was observed when the cells were pretreated with ganglioside GM3. In contrast, the increase in ricin biding sites caused by pretreatment of the cells with neuraminidase was accompanied by increase in ricin cytotoxicity. These differences may be related to observed differences in the rate of ricin-endocytosis by native and ganglioside-treated cells.

Internalization of Clostridium difficile cytotoxin into cultured human lung fibroblasts

In cultured human lung fibroblasts treated with Clostridium difficile cytotoxin, the latency before appearance of the cytopathogenic effect was dose-related with a minimum of 45 min. At 37 degrees C, the toxin was accessible on all cells to inactivation with trypsin or neutralization with antitoxin during the first tenth of the latency. At 0 degrees C, the toxin was accessible considerably longer. The cytopathogenic effect was reversibly prevented by the lysosomotropic agents chloroquine and ammonium chloride, which had to be added within one-fifth of the latency to protect all cells. In the presence of chloroquine, but not of ammonium chloride, the time period during which the toxin remained amenable to neutralization with antitoxin was prolonged. The protective effect of ammonium chloride was not influenced by dropping the extracellular pH to 4.5, but that of chloroquine was abolished. The expression of the intoxication was not affected by inhibitors of the DNA, RNA or protein synthesis. Inhibitors of the energy metabolism prevented the cytopathogenic effect when added before the last phase of the latency. The results suggest that expression of the cytopathogenic effect requires internalization of the toxin, and that metabolic energy but no macromolecular synthesis is needed for the action of the toxin after this internalization.

Cholera toxin B-subunit protects mammalian cells from ricin and abrin toxicity

The glycoproteins ricin and abrin intoxicate cells by inhibiting protein synthesis. Pretreatment of HeLa cells with cholera toxin partially protects them from ricin and abrin activity. The involvement in this phenomenon of the various effects of cholera toxin, namely, redistribution of membrane receptors elicited from protomer B and increasing cyclic AMP concentrations induced by protomer A, were studied. Substances able to enhance cyclic AMP concentrations do not affect ricin and abrin activity, while protomer B alone protects cells. In addition, the effects of several lectins on ricin or abrin toxicity were examined. Almost complete prevention of ricin or abrin activity was obtained using concanavalin A (Con A) and wheat germ agglutinin (WGA). Conversely, neither succinyl Con A nor Ulex europeus agglutinin (UEA) affected the cellular response. Both protomer B of cholera toxin and Con A did not alter the binding of ricin or abrin; they seem to protect cells by altering membrane structure.