Oral Supplementation with Bovine Colostrum Decreases Intestinal Permeability and Stool Concentrations of Zonulin in Athletes.

Increased intestinal permeability has been implicated in various pathologies, has various causes, and can develop during vigorous athletic training. Colostrum bovinum is a natural supplement with a wide range of supposed positive health effects, including reduction of intestine permeability. We assessed influence of colostrum supplementation on intestinal permeability related parameters in a group of 16 athletes during peak training for competition. This double-blind placebo-controlled study compared supplementation for 20 days with 500 mg of colostrum bovinum or placebo (whey). Gut permeability status was assayed by differential absorption of lactulose and mannitol (L/M test) and stool zonulin concentration. Baseline L/M tests found that six of the participants (75%) in the colostrum group had increased intestinal permeability. After supplementation, the test values were within the normal range and were significantly lower than at baseline. The colostrum group Δ values produced by comparing the post-intervention and baseline results were also significantly lower than the placebo group Δ values. The differences in stool zonulin concentration were smaller than those in the L/M test, but were significant when the Δ values due to intervention were compared between the colostrum group and the placebo group. Colostrum bovinum supplementation was safe and effective in decreasing of intestinal permeability in this series of athletes at increased risk of its elevation.

Inhibition of Cholera Toxin and Other AB Toxins by Polyphenolic Compounds.

Cholera toxin (CT) is an AB-type protein toxin that contains a catalytic A1 subunit, an A2 linker, and a cell-binding B homopentamer. The CT holotoxin is released into the extracellular environment, but CTA1 attacks a target within the cytosol of a host cell. We recently reported that grape extract confers substantial resistance to CT. Here, we used a cell culture system to identify twelve individual phenolic compounds from grape extract that inhibit CT. Additional studies determined the mechanism of inhibition for a subset of the compounds: two inhibited CT binding to the cell surface and even stripped CT from the plasma membrane of a target cell; two inhibited the enzymatic activity of CTA1; and four blocked cytosolic toxin activity without directly affecting the enzymatic function of CTA1. Individual polyphenolic compounds from grape extract could also generate cellular resistance to diphtheria toxin, exotoxin A, and ricin. We have thus identified individual toxin inhibitors from grape extract and some of their mechanisms of inhibition against CT.

In Vitro Inhibition of Cholera Toxin Production in Vibrio cholerae by Methanol Extract of Sweet Fennel Seeds and Its Components.

A newly emerged Vibrio cholerae O1 El Tor variant strain with multidrug resistance is considered a threat to public health. Recent strategies to suppress virulence factors production instead of bacterial growth may lead to less selective pressure for the emergence of resistant strains. The use of spices and their active constituents as the inhibitory agents against cholera toxin (CT) production in V. cholerae may be an alternative approach to treat cholera. In this study, we examined the potential of sweet fennel seed (Foeniculum vulgare Miller var. dulce) methanol extract to inhibit CT production in V. cholerae without affecting viability. The methanol extract of sweet fennel seeds significantly inhibited CT production in various V. cholerae strains, regardless of serogroup or biotype. Interestingly, trans-anethole and 4-allylanisole, essential oil components of sweet fennel seeds, also demonstrated similar effects. Here, we report that sub-bactericidal concentrations of sweet fennel seed methanol extract and its major components can drastically inhibit CT production in various V. cholerae strains.

[Effect of plant extracts on cytotoxic activity of Vibrio cholerae hemolysin].

AIM: Study of plant extracts that have the ability to neutralize cytotoxic activity of hemolysin. MATERIALS AND METHODS: Preparations of purified and recombinant V. cholerae eltor hemolysin as well as supernatants of V. cholerae strains were used. Determination ofcytotoxic activity of hemolysin and neutralizing activity of plant extracts were carried out by using cell cultures CHO-K1 and CaCo2. RESULTS: Out of 9 water extracts only 3 - extracts of Rhei rhizome, Limonium gmelinii and Quercus robur neutralized hemolysin in cell culture CHO-K1 and CaCo2, whereas the other extracts--Humulus lupulus, Ocimum basilicum, Chelidonium majus, Juglans regia, Achillea milefolium and Hypericum perforatum did not have anti-cytotoxic effect. Neutralizing properties of extracts are exhibited during their co-incubation with hemolysin preparations and supernatants of V. cholerae strains already within 10 minutes. CONCLUSION: Plant extracts that have anti-cytotoxic activity against hemolysin are perspective for development oftherapeutic-prophylaxis preparations.

Grape extracts inhibit multiple events in the cell biology of cholera intoxication.

Vibrio cholerae produces cholera toxin (CT), an AB5 protein toxin that is primarily responsible for the profuse watery diarrhea of cholera. CT is secreted into the extracellular milieu, but the toxin attacks its Gsα target within the cytosol of a host cell. Thus, CT must cross a cellular membrane barrier in order to function. This event only occurs after the toxin travels by retrograde vesicular transport from the cell surface to the endoplasmic reticulum (ER). The catalytic A1 polypeptide then dissociates from the rest of the toxin and assumes an unfolded conformation that facilitates its transfer to the cytosol by a process involving the quality control system of ER-associated degradation. Productive intoxication is blocked by alterations to the vesicular transport of CT and/or the ER-to-cytosol translocation of CTA1. Various plant compounds have been reported to inhibit the cytopathic activity of CT, so in this work we evaluated the potential anti-CT properties of grape extract. Two grape extracts currently sold as nutritional supplements inhibited CT and Escherichia coli heat-labile toxin activity against cultured cells and intestinal loops. CT intoxication was blocked even when the extracts were added an hour after the initial toxin exposure. A specific subset of host-toxin interactions involving both the catalytic CTA1 subunit and the cell-binding CTB pentamer were affected. The extracts blocked toxin binding to the cell surface, prevented unfolding of the isolated CTA1 subunit, inhibited CTA1 translocation to the cytosol, and disrupted the catalytic activity of CTA1. Grape extract could thus potentially serve as a novel therapeutic to prevent or possibly treat cholera.

A highly specific cell-based high-throughput screening assay for ligands of cyclic adenosine monophosphate receptor protein in gram-negative bacteria.

Quorum sensing is a cell-cell communication process in bacteria that involves the production, release, and subsequent detection of chemical signal molecules called autoinducers. In Vibrio cholerae, multiple input signals activate the expression of the quorum sensing regulator HapR, which acts to repress the expression of virulence factors. We have shown that CRP, the cyclic adenosine monophosphate (cAMP) receptor protein, enhances quorum sensing by activating the biosynthesis of cholera autoinducer 1, the major signaling molecule that contributes to the activation of HapR. Thus, proquorum sensing CRP agonists could inhibit virulence and lead to new drugs to treat severe cholera. In this study, we show that expression of the quorum sensing-regulated luxCDABE operon can be used as a robust readout for CRP activity. Further, we describe and validate a highly specific cell-based luminescence high-throughput screening assay for proquorum sensing CRP ligands. A pilot screen of 9,425 compounds yielded a hit rate of 0.02%, one hit being cAMP itself. The Z' value for this assay was 0.76 and its coefficient of variance 8% for the positive control compound. To our knowledge, this is the first cell-based assay for ligands of the highly conserved CRP protein of Gram-negative bacteria. The use of this assay to screen large chemical libraries could identify lead compounds to treat cholera, as well as small molecules to probe ligand-receptor interactions in the CRP molecule.

[Influence of plant extracts on the activity of cholera toxin of Vibrio cholerae].

AIM: Study the activity of plant extracts against cholera toxin (CT) of Vibrio cholerae O1. MATERIALS AND METHODS: Antitoxic activity of plant extracts was determined by using enzyme immunoassay and CHO-K1 cell culture. RESULTS: 8 water extracts of plants were studied. Extracts of nut, tutsan, milfoil, basil do not have effect on CT activity in EIA or CHO-K1 cell culture. Celandine and rhubarb extracts do not reduce CT immunochemical activity but prevent elongation of CHO-K1 cells. Oak and hop extracts suppress binding in EIA of cholera toxin and GM1 receptors and insignificantly reduce its activity in cell culture. CONCLUSION: Antitoxic activityofplant extracts against CT is perspective for the development of preparations possessing inhibition effect.

Zinc inhibits cholera toxin-induced, but not Escherichia coli heat-stable enterotoxin-induced, ion secretion in human enterocytes.

BACKGROUND: Because zinc deficiency in malnourished children is associated with severe diarrhea, use of zinc supplementation has been proposed as an adjunct to oral rehydration. However, the effects of zinc on enterocyte ion transport are largely unknown. The objective of the present study was to investigate the effects of zinc on transepithelial ion transport under basal conditions and under conditions of enterotoxin-induced ion secretion. METHODS: Ion transport was investigated by monitoring electrical parameters in human intestinal Caco-2 cells that were mounted in Ussing chambers and exposed to increasing concentrations of zinc, both in the absence and presence of either cholera toxin (CT) or Escherichia coli heat-stable enterotoxin (ST). Intracellular cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) concentrations were also determined. RESULTS: The addition of zinc to the luminal or basolateral side of enterocytes induced a chloride-dependent, dose-related decrease in short-circuit current, indicating ion absorption. It also resulted in a substantial reduction in CT-induced ion secretion and in cAMP concentration. E. coli ST-induced ion secretion and cGMP concentration were not affected. Ion absorption peaked at 35 mu mol/L zinc, whereas excess zinc load induced active ion secretion. CONCLUSIONS: By causing a decrease in cAMP concentration, zinc directly promotes ion absorption and substantially reduces CT-induced, but not E. coli ST-induced, ion secretion.

Pasteurella multocida toxin activates human monocyte-derived and murine bone marrow-derived dendritic cells in vitro but suppresses antibody production in vivo.

Pasteurella multocida toxin (PMT) is a potent mitogen for fibroblasts and osteoblastic cells. PMT activates phospholipase C-beta through G(q)alpha, and the activation of this pathway is responsible for its mitogenic activity. Here, we investigated the effects of PMT on human monocyte-derived dendritic cells (MDDC) in vitro and show a novel activity for PMT. In this regard, PMT activates MDDC to mature in a dose-dependent manner through the activation of phospholipase C and subsequent mobilization of calcium. This activation was accompanied by enhanced stimulation of naive alloreactive T cells and dominant inhibition of interleukin-12 production in the presence of saturating concentrations of lipopolysaccharide. Surprisingly, although PMT mimics the activating effects of cholera toxin on human MDDC and mouse bone marrow-derived dendritic cells, we found that PMT is not a mucosal adjuvant and that it suppresses the adjuvant effects of cholera toxin in mice. Together, these results indicate discordant effects for PMT in vitro compared to those in vivo.

Inhibition by apple polyphenols of ADP-ribosyltransferase activity of cholera toxin and toxin-induced fluid accumulation in mice.

The effects of crude polyphenol extracted from immature apples on the enzymatic and biological activities of a cholera toxin (CT) were investigated. When the apple polyphenol extract (APE) was examined for properties to inhibit CT-catalyzed ADP-ribosylation of agmatine, it was found that APE inhibited it in a dose-dependent manner. The concentration of APE to inhibit 50% of the enzymatic activity of CT (15 microg/ml) was approximately 8.7 microg/ml. The APE also diminished CT-induced fluid accumulation in two diarrhea models for in vivo mice. In the ligated ileum loops, 25 microg of APE significantly inhibited fluid accumulation induced by 500 ng of CT. In a sealed mouse model, even when APE was administered orally 10 min after a toxin injection, fluid accumulation was significantly inhibited at a comparable dosage. Lineweaver-Burk analysis demonstrated that APE had negative allosteric effects on CT-catalyzed NAD: agmatine ADP-ribosyltransferase. We fractionated the APE into four fractions using LH-20 Sephadex resin. One of the fractions, FAP (fraction from apple polyphenol) 1, which contains non-catechin polyphenols, did not significantly inhibit the CT-catalyzed ADP-ribosylation of agmatine. FAP2, which contains compounds with monomeric, dimeric, and trimeric catechins, inhibited the ADP-ribosylation only partially, but significantly. FAP3 and FAP4, which consist of highly polymerized catechin compounds, strongly inhibited the ADP-ribosylation, indicating that the polymerized structure of catechin is responsible for the inhibitory effect that resides in APE. The results suggest that polymerized catechin compounds in APE inhibit the biological and enzymatic activities of CT and can be used in a precautionary and therapeutic manner in the treatment of cholera patients.

Experimental evaluation of antitoxic protective effect of new cholera vaccines in mice.

Intraperitoneal immunization of mice and subsequent challenge with purified cholera toxin (CT) were employed to evaluate the anti-cholera toxin protective effect of two new oral cholera vaccines, live CVD 103-HgR and killed B subunit-whole cell (BS-WC). CVD 103-HgR vaccine demonstrated 100% protection of mice against 2.25 LD50 and 70% against 3 LD50 of CT. Mice immunized with BS-WC vaccine were protected against 2.25 and 3 LD50 of CT in 88 and 62% of cases, respectively. All three killed parenteral vaccines failed to protect against CT. We suggest this mouse system for preliminary evaluation of the antitoxic protective activity of cholera vaccines.

The protective activity of tea catechins against experimental infection by Vibrio cholerae O1.

Tea catechins inhibited the fluid accumulation induced by cholera toxin in sealed adult mice. The catechins also reduced fluid accumulation by Vibrio cholerae O1 in ligated intestinal loops of rabbits. These findings suggest that tea catechins may possess protective activity against V. cholerae O1.

The protective activity of tea against infection by Vibrio cholerae O1.

Extracts of black tea exhibited bactericidal activity against Vibrio cholerae O1. The tea extract inhibited the haemolysin activity of V. cholerae O1, El Tor and the morphological changes of Chinese hamster ovary cells induced by cholera toxin. Tea extract also reduced fluid accumulation induced by cholera toxin in sealed adult mice and by V. cholerae O1 in ligated intestinal loops of rabbits. These findings suggest that tea has protective activity against V. cholerae O1.