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PubMed2003

Suitability of binary mixtures of water with aprotic solvents to turn hydroxyl protons of carbohydrate ligands into conformational sensors in NOE and transferred NOE experiments.

The structural analysis of protein-carbohydrate interactions is essential for the long-range aim to sort out entropic/ enthalpic factors in the binding process. Of conspicuous clinical interest, this work can also offer the perspective to devise new classes of therapeuticals which interfere with disease-related glycan recognition. We have shown that it is possible to use exchangeable hydroxyl protons of carbohydrate ligands as conformational sensors for defining their bound-state topology by measurements in dimethyl sulfoxide(d6) (Siebert et al. (2000) ChemBioChem, 1, 181-195). However, the proteins are required to maintain binding capacity in the aprotic solvent. To define conditions to limit its harmful effect on sensitive protein structures while still being able to pick up solvent-exchangeable hydroxyl signals we systematically tested binary solvent mixtures of dimethyl sulfoxide and acetone with water. These solvent mixtures did not preclude to monitor hydroxyl protons of carbohydrate ligands even at temperatures well above 0 degrees C. Notably, hydrogen bonding of the two tested disaccharides (Galbeta1-4Glcalpha/beta and Galalpha1-3Galalpha/beta or Galalpha1-3Galbeta1-OCH(3)), which are common lectin ligands, resembled the situation under physiological conditions. Also, a refined topological description for hydroxyl positioning could be achieved for Galalpha1-3Gal. At least equally important, this approach worked for elucidation of the mistletoe-lectin-bound topology of lactose in its syn-conformation with indication for formation of a characteristic interresidual hydrogen bond. These measurements were performed in a binary dimethyl sulfoxide(d6):water mixture (6:4 ratio, v/v) at -12 degrees C and encourage to pursue this line of investigation by monitoring in the course of stepwise temperature increases. Our experiments reveal that binary mixtures have favorable properties for the conformational analysis of the free- and bound-state topologies of bioactive ligands.

Acetone↗
PubMed2003

X-ray crystallographic studies of protein-ligand interactions.

X-ray crystallography enables details of covalent and non-covalent interactions to be analysed quantitatively in three dimensions, thus providing the basis for the understanding of binding of ligands to proteins as well as modes of action such as cell-surface binding. This article is concerned with current methods employed for the X-ray analysis of protein structures complexed with ligands. It deals mainly with 'what can be done' in current research, rather than providing details of 'how to do it'. In recent years significant advances have been made in a variety of techniques: growing protein crystals from very small samples by scanning a wide range of conditions; X-ray intensity data collection and measurement through the use of charge-coupled devices and high-intensity, versatile synchrotron sources; cryo-crystallography which both stabilizes the crystals and provides improved data; methods for analysing and interpreting the structures, dependent, at least in part, on both structural and sequence databases; and improvements in hardware and software. To illustrate the type of results achievable two examples involving protein-sugar interactions are discussed: (i) SNAII (the lectin Sambucus nigra agglutinin-II from elder) N-terminal sugar-binding site where terminal sugar units in a glycosylation chain from a symmetry-related molecule bind and (ii) MLI (mistletoe lectin I) C-terminal sugar-binding site with lactose.

Binding Sites↗
PubMed2000

Mucosal immunogenicity of plant lectins in mice.

The mucosal immunogenicity of a number of plant lectins with different sugar specificities was investigated in mice. Following intranasal (i.n.) or oral administration, the systemic and mucosal antibody responses elicited were compared with those induced by a potent mucosal immunogen (cholera toxin; CT) and a poorly immunogenic protein (ovalbumin; OVA). After three oral or i.n. doses of CT, high levels of specific serum antibodies were measured and specific IgA was detected in the serum, saliva, vaginal wash, nasal wash and gut wash of mice. Immunization with OVA elicited low titres of serum IgG but specific IgA was not detected in mucosal secretions. Both oral and i.n. delivery of all five plant lectins investigated ¿Viscum album (mistletoe lectin 1; ML-1), Lycospersicum esculentum (tomato lectin; LEA), Phaseolus vulgaris (PHA), Triticum vulgaris (wheat germ agglutinin (WGA), Ulex europaeus I (UEA-1) stimulated the production of specific serum IgG and IgA antibody after three i. n. or oral doses. Immunization with ML-1 induced high titres of serum IgG and IgA in addition to specific IgA in mucosal secretions. The response to orally delivered ML-1 was comparable to that induced by CT, although a 10-fold higher dose was administered. Immunization with LEA also induced high titres of serum IgG, particularly after i. n. delivery. Low specific IgA titres were also detected to LEA in mucosal secretions. Responses to PHA, WGA and UEA-1 were measured at a relatively low level in the serum, and little or no specific mucosal IgA was detected.

Administration, Intranasal↗
PubMed2001

The identification of plant lectins with mucosal adjuvant activity.

To date, the most potent mucosal vaccine adjuvants to be identified have been bacterial toxins. The present data demonstrate that the type 2 ribosome-inactivating protein (type 2 RIP), mistletoe lectin I (ML-I) is a strong mucosal adjuvant of plant origin. A number of plant lectins were investigated as intranasal (i.n.) coadjuvants for a bystander protein, ovalbumin (OVA). As a positive control, a potent mucosal adjuvant, cholera toxin (CT), was used. Co-administration of ML-I or CT with OVA stimulated high titres of OVA-specific serum immunoglobulin G (IgG) in addition to OVA-specific IgA in mucosal secretions. CT and ML-I were also strongly immunogenic, inducing high titres of specific serum IgG and specific IgA at mucosal sites. None of the other plant lectins investigated significantly boosted the response to co-administered OVA. Immunization with phytohaemagglutinin (PHA) plus OVA elicited a lectin-specific response but did not stimulate an enhanced response to OVA compared with the antigen alone. Intranasal delivery of tomato lectin (LEA) elicited a strong lectin-specific systemic and mucosal antibody response but only weakly potentiated the response to co-delivered OVA. In contrast, administration of wheatgerm agglutinin (WGA) or Ulex europaeus lectin 1 (UEA-I) with OVA stimulated a serum IgG response to OVA while the lectin-specific responses (particularly for WGA) were relatively low. Thus, there was not a direct correlation between immunogenicity and adjuvanticity although the strongest adjuvants (CT, ML-I) were also highly immunogenic.

Adjuvants, Immunologic↗
PubMed2001

Cytotoxic activity of moronic acid and identification of the new triterpene 3,4-seco-olean-18-ene-3,28-dioic acid from Phoradendron reichenbachianum.

The cytotoxic compound moronic acid (1) and the new tetracyclic triterpene 3,4-seco-olean-18-ene-3,28-dioic acid (2), were isolated from the aerial parts of the medicinal plant Phoradendron reichenbachianum (mistletoe, Loranthaceae) through a bioassay-guided fractionation. In addition, squalene, glycerol trilinoleate, morolic acid, betulonaldehyde, betulinaldehyde, alpha-germanicol, lupeol, beta-sitosterol and beta-sitosteril glucopyranoside, were identified in this plant species. The structures were elucidated on the basis of chemical and spectroscopic evidence.

Antineoplastic Agents, Phytogenic↗
PubMed2003

Identification of the ricin lipase site and implication in cytotoxicity.

Ricin is a heterodimeric plant toxin and the prototype of type II ribosome-inactivating proteins. Its B-chain is a lectin that enables cell binding. After endocytosis, the A-chain translocates through the membrane of intracellular compartments to reach the cytosol where its N-glycosidase activity inactivates ribosomes, thereby arresting protein synthesis. We here show that ricin possesses a functional lipase active site at the interface between the two subunits. It involves residues from both chains. Mutation to alanine of catalytic serine 221 on the A-chain abolished ricin lipase activity. Moreover, this mutation slowed down the A-chain translocation rate and inhibited toxicity by 35%. Lipase activity is therefore required for efficient ricin A-chain translocation and cytotoxicity. This conclusion was further supported by structural examination of type II ribosome-inactivating proteins that showed that this lipase site is present in toxic (ricin and abrin) but is altered in nontoxic (ebulin 1 and mistletoe lectin I) members of this family.

Enzyme Activation↗
PubMed2004

Immunological implications of the use of plant lectins for drug and vaccine targeting to the gastrointestinal tract.

Plant lectins are under consideration as targeting agents to enhance the efficacy of orally administered drugs and vaccines. A significant issue that must be considered is the immunogenicity of these molecules since an immune response to the targeting agent may interfere with its ability to interact with the epithelium. In contrast, the ability of certain lectins to activate the immune system may be exploited in the delivery of vaccines. We previously demonstrated that plant lectins vary widely in their immunogenicity and in particular that mistletoe lectins (ML) I, II and II (MLI, MLII, MLIII) are potent immunogens when administered nasotracheally. Here, we measured immune responses following oral delivery of the MLs and assessed their ability to enhance responses to a co-administered antigen to determine if the molecules possess adjuvant activity. Oral administration of the lectins induced potent lectin-specific systemic and mucosal antibody responses. In addition, each of the three lectins possessed adjuvant activity when delivered orally together with ovalbumin (OVA). The lectins enhanced both serum and mucosal antibody responses to the co-delivered antigen. This shows for the first time that MLI, MLII and MLIII possess adjuvant activity when administered orally and may provide a platform for the generation of effective mucosal adjuvants.

Administration, Oral↗
PubMed2002

Botanical medicines for the treatment of cancer: rationale, overview of current data, and methodological considerations for phase I and II trials.

There appears to be exceptional and growing public enthusiasm for botanical, or "herbal", medicines, especially amongst cancer patients. This has recently begun to be matched by increasing scientific attention. Whilst it is known that plant extracts are active against cancer, the standard approach has been to isolate, synthesize and administer the single chemical compound thought responsible for this effect. However, different components in a botanical may have synergistic activities. There is also some evidence that the presence of multiple compounds in a botanical extract can buffer the toxic effects of a single constituent. Though many of the botanicals popular among patients are probably not of benefit (e.g. Mistletoe, Pau D'arco), several botanicals have shown promise in Phase III (Sho-saiko-to, PSK) or Phase II (PC-SPES) trial. Quality control of botanicals poses significant challenges: small differences in genetics, soil, temperature, moisture and time of harvesting can lead to significant differences in the concentration of important constituents. Phase I and II methodology is also problematic: botanicals have low toxicity and are unlikely to cause rapid tumor regression. There is currently minimal regulation of botanical medicines.

Antineoplastic Agents, Phytogenic↗
PubMed1999

Lactose-containing starburst dendrimers: influence of dendrimer generation and binding-site orientation of receptors (plant/animal lectins and immunoglobulins) on binding properties.

Starburst glycodendrimers offer the potential to serve as high-affinity ligands for clinically relevant sugar receptors. In order to define areas of application, their binding behavior towards sugar receptors with differential binding-site orientation but identical monosaccharide specificity must be evaluated. Using poly(amidoamine) starburst dendrimers of five generations, which contain the p-isothiocyanato derivative of p-aminophenyl-beta-D-lactoside as ligand group, four different types of galactoside-binding proteins were chosen for this purpose, i.e., the (AB)(2)-toxic agglutinin from mistletoe, a human immunoglobulin G fraction, the homodimeric galectin-1 with its two binding sites at opposite ends of the jelly-roll-motif-harboring protein and monomeric galectin-3. Direct solid-phase assays with surface-immobilized glycodendrimers resulted in obvious affinity enhancements by progressive core branching for the plant agglutinin and less pronounced for the antibody and galectin-1. High density of binding of galectin-3 with modest affinity increases only from the level of the 32-mer onwards points to favorable protein-protein interactions of the monomeric lectin and a spherical display of the end groups without a major share of backfolding. When the inhibitory potency of these probes was evaluated as competitor of receptor binding to an immobilized neoglycoprotein or to asialofetuin, a marked selectivity was detected. The 32- and 64-mers were second to none as inhibitors for the plant agglutinin against both ligand-exposing matrices and for galectin-1 on the matrix with a heterogeneous array of interglycoside distances even on the per-sugar basis. In contrast, a neoglycoprotein with the same end group was superior in the case of the antibody and, less pronounced, monomeric galectin-3. Intimate details of topological binding-site presentation and the ligand display on different generations of core assembly are major operative factors which determine the potential of dendrimers for applications as lectin-targeting device, as attested by these observations.

Animals↗
PubMed1993

Unproven methods in cancer treatment.

The nature-based and nontoxic image makes application of unproven methods in oncology attractive in contrast to application of a mechanized scientific medicine. The application frequency of these treatments ranges from 10% to greater than 60%. Increasingly, the promoters try to create a scientific impression through a pseudologic cancer theory, a harmless diagnostic test, and a holistic treatment of every cancer. Of the big variety of unproven methods, which are summarized in 11 groups in this review, the following are discussed: anthroposophic and other mistletoe preparations; homeopathy; Maharishi Ayur-Veda; unproven anticancer diets; orthomolecular medicine, including ascorbic acid; and methods supposedly stimulating unspecific and specific defense mechanisms. In conclusion, physicians should beware of and have knowledge of currently used unproven cancer treatments for epidemiologic, social, economic, and scientific reasons.

Complementary Therapies↗
PubMed1985

Holiday hazards.

Presented is a selective review of the toxicities of various plants, decorations, and miscellaneous items popularly used during the holiday season. Particularly hazardous agents include mistletoe, holly, bubble lights, fireplace flame colors, alkaline batteries, and mothballs. Specific questions regarding management of exposure to these items should be referred to regional poison control centers. Avoidance is the most effective treatment.

Child↗
PubMed2006

Developmental therapeutics: review of biologically based CAM therapies for potential application in children with cancer: part I.

This article is a review of the status of biologically based complementary and alternative medicine (CAM) therapies that have potential anticancer activity with a focus on those agents that may be active in childhood cancer. The review presented in 2 parts includes the descriptions of the mechanisms that underlie their effects, the manner by which these agents are identified and evaluated and discussion of some of the limitations of current research. The first part introduces the topic of biologically based CAM therapies. The discussion includes a description the discovery biologically based products for cancer, the classification of these compounds and their use from the perspectives of the Ayurvedic and traditional Chinese medicine systems. Issues associated with evidence-based research of compounds used in these practices are addressed. The second part focuses on preclinical and clinical studies of specific herbs or natural products and their bioactive constituents that demonstrate potential in cancer therapeutics. Turmeric, mistletoe, green tea, ginseng, mushrooms, and micronutrients are representative of compounds that exert their effects through mechanisms attributed to specific chemical classes. The section concludes with a discussion of status of clinical trials of biologically based CAM therapeutics for cancer and the future direction of research.

Child↗
PubMed2005

Gene transfer from a parasitic flowering plant to a fern.

The rattlesnake fern (Botrychium virginianum (L.) Sw.) is obligately mycotrophic and widely distributed across the northern hemisphere. Three mitochondrial gene regions place this species with other ferns in Ophioglossaceae, while two regions place it as a member of the largely parasitic angiosperm order Santalales (sandalwoods and mistletoes). These discordant phylogenetic placements suggest that part of the genome in B. virginianum was acquired by horizontal gene transfer (HGT), perhaps from root-parasitic Loranthaceae. These transgenes are restricted to B. virginianum and occur across the range of the species. Molecular and life-history traits indicate that the transfer preceded the global expansion of B. virginianum, and that the latter may have happened very rapidly. This is the first report of HGT from an angiosperm to a fern, through either direct parasitism or the mediation of interconnecting fungal symbionts.

Ferns↗
PubMed2003

Structure of viscotoxin A3: disulfide location from weak SAD data.

The crystal structure of viscotoxin A3 (VT A3) extracted from European mistletoe (Viscum album L.) has been solved using the anomalous diffraction of the native S atoms measured in-house with Cu Kalpha radiation to a resolution of 2.2 A and truncated to 2.5 A. A 1.75 A resolution synchrotron data set was used for phase expansion and refinement. An innovation in the dual-space substructure-solution program SHELXD enabled the individual S atoms of the disulfide bonds to be located using the Cu Kalpha data; this resulted in a marked improvement in the phasing compared with the use of super-S atoms. The VT A3 monomer consists of 46 amino acids with three disulfide bridges and has an overall fold resembling the canonical architecture of the alpha- and beta-thionins, a capital letter L. The asymmetric unit consists of two monomers related by a local twofold axis and held together by hydrophobic interactions between the monomer units. One phosphate anion (confirmed by 31P-NMR and MS) is associated with each monomer.

Binding Sites↗
PubMed2004

Anti-inflammatory effect of Viscum album agglutinin-I (VAA-I): induction of apoptosis in activated neutrophils and inhibition of lipopolysaccharide-induced neutrophilic inflammation in vivo.

Viscum album agglutinin-I (VAA-I) is a plant lectin which possesses antitumoral properties. This lectin is also known for its immunostimulatory effects when used at low concentrations (1-100 ng/ml). We have demonstrated recently that VAA-I is a potent inducer of human neutrophil apoptosis in vitro when used at higher concentrations. The role of VAA-I on activated neutrophils has not so far been investigated and its potential proinflammatory properties in vivo are poorly documented. Herein, we demonstrated that VAA-I (1000 ng/ml) induces apoptosis in lipopolysaccharide (LPS)-treated human neutrophils in vitro as well as in murine neutrophils isolated from lipopolysaccharide (LPS)-induced neutrophil influx. Using this model, we found that administration of VAA-I (100 or 1000 ng/ml) did not induce an inflammatory response. However, when used at 1 or 10 ng/ml, VAA-I was found to significantly induce a transitory inflammatory response, based on an increased leucocyte infiltration (>98% neutrophils). Also, we found that VAA-I inhibits LPS-induced neutrophil influx when administered simultaneously with LPS. In such conditions, some characteristic apoptotic neutrophils were observed in the pouch. Unlike LPS, which increased the production of some cytokines, VAA-I (1 or 10 ng/ml) did not increase the production of tumour necrosis factor (TNF)-alpha, interleukin (IL)-1Ra, IL-1alpha, IL-beta, IL-8, IL-10 or IL-12 (p70) in human neutrophils. We conclude that VAA-I possesses the ability to induce apoptosis of preactivated neutrophils at a concentration that does not induce a proinflammatory response. Moreover, we conclude that VAA-I can inhibit a LPS-induced proinflammatory response in vivo. These data may provide new clinical perspectives in future mistletoe therapy and favour its potential utilization based on anti-inflammatory activity that at first appears contradictory with its use as immunostimulant.

Animals↗
PubMed1981

Thionins: plant peptides that modify membrane permeability in cultured mammalian cells.

Thionins, which are high-sulphur polypeptides present in the endosperm of wheat and related species, have ben found to prevent growth and to inhibit macromolecular synthesis in cultured mammalian cells. Baby hamster kidney (BHK) cells were markedly more sensitive to thionins than the other cell lines tested (monkey CV1, mouse L, human HeLa). A thionin concentration of 5 microgram/ml (1 microM) completely blocked translation in BHK cells. It was later found that omission of both calcium and magnesium ions from the medium strongly enhanced the inhibitory effects of thionins (BHK cells, 80% inhibition, 0.5 microgram/ml). Several lines of evidence indicate that thionins might act at the membrane level. Indeed, both the 86Rb+ content and the nucleotide pool of BHK cells were drastically decreased at thionin concentrations that inhibited translation. In addition, thionin concentrations that did not affect macromolecular synthesis in these cells, allowed inhibition of translation by antibiotics, such as hygromycin B, that are not able to cross the cell plasma membrane by themselves. Our results suggest that the inhibition of protein, RNA and DNA synthesis in BHK cells might be a consequence of membrane leakiness induced by thionin treatment. In this respect, particularly striking was the parallelism found between 86Rb+ leakage and inhibition of protein synthesis by treatment with different genetic variants of thionins (alpha 1 purothionin, alpha 2 purothionin, beta purothionin from wheat; hordothionin from barley), as well as with the viscotoxins, which are homologous polypeptides from the European mistletoe.

Animals↗
PubMed1976

The amino acid sequence of wheat beta-purothionin.

The complete amino acid sequence of beta-purothionin, a low molecular weight, very basic, protein isolated from wheat endosperm material, has been determined. beta-purothionin is toxic to some bacteria, to yeasts, and to animals when injected. The protein contains 45 amino acid residues and has a molecular weight of 4913. The 8 cysteine and 10 basic residues are distributed throughout the molecule. The primary structure of the protein shows considerable homology to those of the viscotoxins, which are toxic, small, basic proteins found in the leaves and stems of European mistletoe (Viscum album L.).

Amino Acid Sequence↗
PubMed2003

Carl Freiherr von Tubeuf: pioneer in biological control of plant diseases.

Carl von Tubeuf, a founder of plant pathology in Europe, pioneered biological control of a major plant disease and introduced the term "biological control" to plant pathology. His book on plant diseases was one of the first to be published in English. He was proficient in many areas, and his interests included plant diseases, mycology, forest insects, white pine blister rust, the mistletoes, plant protection laws, and nature conservation.

Europe↗