A novel plant toxin, persin, with in vivo activity in the mammary gland, induces Bim-dependent apoptosis in human breast cancer cells

Phytochemicals have provided an abundant and effective source of therapeutics for the treatment of cancer. Here we describe the characterization of a novel plant toxin, persin, with in vivo activity in the mammary gland and a p53-, estrogen receptor-, and Bcl-2-independent mode of action. Persin was previously identified from avocado leaves as the toxic principle responsible for mammary gland-specific necrosis and apoptosis in lactating livestock. Here we used a lactating mouse model to confirm that persin has a similar cytotoxicity for the lactating mammary epithelium. Further in vitro studies in a panel of human breast cancer cell lines show that persin selectively induces a G(2)-M cell cycle arrest and caspase-dependent apoptosis in sensitive cells. The latter is dependent on expression of the BH3-only protein Bim. Bim is a sensor of cytoskeletal integrity, and there is evidence that unique structure of the compound, persin could represent a novel class of microtubule-targeting agent with potential specificity for breast cancers.

Attachment of Shiga toxigenic Escherichia coli to beef muscle and adipose tissue

Shiga toxigenic Escherichia coli (STEC) serotypes are important foodborne pathogens that cause gastrointestinal disease worldwide. An understanding of how STEC strains attach to surfaces may provide insight into the potential persistence of and contamination with STEC in food environments. The initial attachment of a selection of STEC serotypes to beef muscle and adipose tissue was evaluated for isolates grown in planktonic and sessile culture. Initial experiments were performed to determine whether attachment differed among STEC strains and between the two modes of growth. Viable counts were obtained for loosely and strongly attached cells, and the strength of attachment (S-r) was calculated. All bacterial isolates grown in sessile culture attached in higher numbers to muscle and adipose tissue than did bacteria in planktonic cultures. For all attachment assays performed, mean concentrations for loosely attached cells were consistently higher than concentrations for strongly attached cells. The mean concentrations for strongly attached bacteria for planktonic and sessile cultures were significantly higher (P < 0.05) on adipose than on muscle tissue. However, some strains of STEC, particularly those from sessile culture, did not differ in their attachment to muscle or adipose tissue. S-r values were not significantly different (P > 0.05) among STEC isolates for all assays. No correlation was found between bacterial hydrophobicity and surface charge values (previously determined) and production of surface structures, viable counts, and S-r values. STEC grown in planktonic and sessile culture seems to behave differently with respect to attachment to muscle and adipose tissue. Cells in sessile culture may have a greater potential to strongly attach to meat surfaces.

Biodegradation of the cyanobacterial toxin microcystin LR in natural water and biologically active slow sand filters

A bacterium (MJ-PV) previously demonstrated to degrade the cyanobacterial toxin microcystin LR, was investigated for bioremediation applications in natural water microcosms and biologically active slow sand filters. Enhanced degradation of microcystin LR was observed with inoculated (1 x 10(6) cell/mL) treatments of river water dosed with microcystin LR (> 80% degradation within 2 days) compared to uninoculated controls. Inoculation of MJ-PV at lower concentrations (1 x 10(2)-1 x 10(5)cells/mL) also demonstrated enhanced microcystin LR degradation over control treatments. Polymerase chain reactions (PCR) specifically targeting amplification of 16S rDNA of MJ-PV and the gene responsible for initial degradation of microcystin LR (mlrA) were successfully applied to monitor the presence of the bacterium in experimental trials. No amplified products indicative of an endemic MJ-PV population were observed in uninoculated treatments indicating other bacterial strains were active in degradation of microcystin LR, Pilot scale biologically active slow sand filters demonstrated degradation of microcystin LR irrespective of MJ-PV bacterial inoculation. PCR analysis detected the MJ-PV population at all locations within the sand filters where microcystin degradation was measured. Despite not observing enhanced degradation of microcystin LR in inoculated columns compared to uninoculated column, these studies demonstrate the effectiveness of a low-technology water treatment system like biologically active slow sand filters for removal of microcystins from reticulated water supplies. Crown Copyright (c) 2006 Published by Elsevier Ltd. All rights reserved.

Toxin insights into nicotinic acetylcholine receptors

Venomous species have evolved cocktails of bioactive peptides to facilitate prey capture. Given their often exquisite potency and target selectivity, venom peptides provide unique biochemical tools for probing the function of membrane proteins at the molecular level. in the field of the nicotinic acetylcholine receptors (nAChRs), the subtype specific snake alpha-neurotoxins and cone snail alpha-conotoxins have been widely used to probe receptor structure and function in native tissues and recombinant systems. However, only recently has it been possible to generate an accurate molecular view of these nAChR-toxin interactions. Crystal structures of AChBP, a homologue of the nAChR ligand binding domain, have now been solved in complex with alpha-cobratoxin, alpha-conotoxin PnIA and alpha-conotoxin Iml. The orientation of all three toxins in the ACh binding site confirms many of the predictions obtained from mutagenesis and docking simulations on homology models of mammalian nAChR. The precise understanding of the molecular determinants of these complexes is expected to contribute to the development of more selective nAChR modulators. In this commentary, we review the structural data on nAChR-toxin interactions and discuss their implications for the design of novel ligands acting at the nAChR. (c) 2006 Elsevier Inc. All rights reserved.

Genotoxicity investigation of chlorinated degradation products of a cyanobacterial toxin, cylindrospermopsin

Cylindrospermopsin (CYN), a potent cyanobacterial hepatotoxin produced by Cylindrospermopsis raciborskii and other cyanobacteria, is regularly found in water supplies in many parts of the world and has been associated with the intoxication of humans and livestock.Water treatment via chlorination can degrade the toxin effectively but result in the production of several byproducts. In this study, male and female Balb/c mice were injected via the intraperitoneal (IP) route with a single dose of 10 mg/kg 5-chlorouracil and 10 mg/kg 5-chloro-6-hydroxymethyluracil; these two compounds are the predicted chlorinated degradation products of CYN.DNA was isolated from the mouse livers and examined for strand breakage by alkaline gel electrophoresis (pH 12). The median molecular length (MML) of the DNA distributed in the gel was determined by estimating the midpoint of the DNA size distribution by densitometry. The toxicity of 5-chlorouracil (as measured by DNA strand breakage) was significantly influenced by time from dosing. There was no significant difference in MML between mice dosed with 5-chloro-6-hydroxymethyluracil and the controls. In another experiment, mice were dosed with 0, 0.1, 1, 10 and 100 mg/kg body weight 5-chlorouracil and 0, 0.1, 1, 10 and 20 mg/kg 5-chloro-6-hydroxymethyluracil via IP injection. The heart, liver, kidney, lung and spleen were removed, fixed and examined under electron microscopy. Liver was the main target organ. The EM results revealed marked distortion on the nuclear membrane of liver cells in mice dosed with 1.0 mg/kg 5-chlorouracil or 10 mg/kg 5-chloro-6-hydroxymethyluracil, or higher.