Apoptotic cell death induced by physarumin (hemagglutinin from myxomycete, Physarum polycephalum)

The recognition of N-glycans by the lectin ArtinM mediates cell death of a human myeloid leukemia cell line

ArtinM, a d-mannose-binding lectin from Artocarpus heterophyllus (jackfruit), interacts with N-glycosylated receptors on the surface of several cells of hematopoietic origin, triggering cell migration, degranulation, and cytokine release. Because malignant transformation is often associated with altered expression of cell surface glycans, we evaluated the interaction of ArtinM with human myelocytic leukemia cells and investigated cellular responses to lectin binding. The intensity of ArtinM binding varied across 3 leukemia cell lines: NB4>K562>U937. The binding, which was directly related to cell growth suppression, was inhibited in the presence of Manα1-3(Manα1-6)Manβ1, and was reverted in underglycosylated NB4 cells. ArtinM interaction with NB4 cells induced cell death (IC₅₀ = 10 µg/mL), as indicated by cell surface exposure of phosphatidylserine and disruption of mitochondrial membrane potential unassociated with caspase activation or DNA fragmentation. Moreover, ArtinM treatment of NB4 cells strongly induced reactive oxygen species generation and autophagy, as indicated by the detection of acidic vesicular organelles in the treated cells. NB4 cell death was attributed to ArtinM recognition of the trimannosyl core of N-glycans containing a ß1,6-GlcNAc branch linked to α1,6-mannose. This modification correlated with higher levels of N-acetylglucosaminyltransferase V transcripts in NB4 cells than in K562 or U937 cells. Our results provide new insights into the potential of N-glycans containing a β1,6-GlcNAc branch linked to α1,6-mannose as a novel target for anti-leukemia treatment.

Apoptosis induction by Maackia amurensis agglutinin in childhood acute lymphoblastic leukemic cells

Malignant transformation is known to be associated with changes in cell surface carbohydrate-architecture, which can be detected by lectins. In the present study, Maackia amurensis agglutinin (MAA), specific for NeuNAcalpha(2-->3)Gal/GalNAc showed strong binding with lymphoblasts of children having acute lymphoblastic leukemia (ALL) as compared to cells from children with non-hematological disorders ("Controls"). MAA recognized a 66 kDa sialoglycoprotein present in membrane fraction of ALL cells. Moreover, MAA induced apoptosis in ALL cells was found to be reduced significantly in presence of GM2/IgG(MAA). Thus, MAA has a potential to be used as diagnostic and therapeutic agent in case of childhood-ALL.

Echinococcus granulosus: regulation of leukocyte growth by living protoscoleces from horses, sheep, and cattle

To determine whether living hydatid tissue can, like hydatid fluid, regulate leukocyte growth, T-cell, B-cell, and macrophage lines were cocultured with protoscoleces of Echinococcus granulosus and their growth was compared with that of control cultures by thymidine uptake estimates and chemiluminescent assays of cell number. Protoscoleces supported mitosis of IL-1-deprived D10 T cells, but did not increase D10 count. The action of protoscoleces was affected by the species and organ of their origin and the length of time in culture. Unusually marked mitotic reaction, unaffected by parasite age and origin, was recorded in the B-cell line, BSM, also without commensurate count increase, indicating that induced mitosis resulted in cell loss. It is concluded that protoscoleces can induce mitosis in B and T cells of particular lineages and that this is a potential means of producing the pathological proliferation and depletion of B- and T-cell areas which characterize local reaction to hydatids.

Growth kinetics of leukocyte cell lines cultured with hydatid fluid of Echinococcus granulosus equinus

Oxidation of 3,(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and tritiated thymidine uptake were used to measure, respectively, the viable cell count and the S-phase activity of D10, B9, A20 and p388d leukocytic cell lines cultured in the presence of varying concentrations of fluid from fertile and infertile hydatid cysts of Echinococcus granulosus equinus. Exposure to hydatid fluid raised or lowered the entry of D10 cells into S-phase depending on the concentration of the fluid and of the supporting cytokines. Enlargement of the S-phase population was unaccompanied by increase in viable count indicating that the mitotic cycles induced by hydatid products were not completed. A similar conclusion was reached in respect of the p388d monocytic line, and both changes appear consistent with those occurring in histopathology in vivo. By contrast, the main effect on B9 and A20 B cells was inhibition of entry into S-phase.

Echinococcus granulosus: assays for hydatid immunoregulatory factors using established lymphoid cell lines

Mitosis, mitochondrial metabolic rate and proliferation were measured in established lymphoid cell lines exposed to chromatographic fractions of equine Echinococcus granulosus hydatid fluid. In several cell lines, one or more of the three parameters were modified by the exposure. As an assay for potential immunoregulatory activity, the method was simple and repeatable. The following novel observations were made: (1) Mitotic reaction was found among lines of T-cell, B-cell and macrophage origin; (2) mitosis was accompanied by proliferation in the B-cell lines, B9 and A20, and in the macrophage lines, HL-60 and P388d. With mitotically responsive T-cells, proliferation was slight in CTLL-2 and absent in D10, implying cell-cycle modification; (3) mitotic responsiveness tended to occur in cell lines with mature characteristics; (4) among cytokine-dependent cell lines, hydatid fluid FPLC fraction 1 mimicked IL-1 and several fractions mimicked IL-2 and IL-6 in the maintenance of mitosis; and (5) there was significant statistical interaction between the influences of mammalian cytokines and hydatid fluid fractions, implying that the propensity of antigenically unprimed lymphoid cells to be regulated by E. granulosus is conditioned by cytokine activity.