Black Tea Theaflavin Detoxifies Metabolic Toxins in the Intestinal Tract of Mice.

SCOPE: This study is to determine the in vivo efficacy of black tea theaflavin (TF) to detoxify two metabolic toxins, ammonia and methylglyoxal (MGO), in mice METHODS AND RESULTS: Under in vitro conditions, TF is able to react with ammonia, MGO, and hydrogen peroxide to produce its aminated, MGO conjugated, and oxidized products, respectively. In TF-treated mice, the aminated TF, the MGO conjugates of TF and aminated TF, and the oxidized TF are searched using LC-MS/MS. The results provide the first in vivo evidence that the unabsorbed TF is able to trap ammonia to form the aminated TF; furthermore, both TF and the aminated TF have the capacity to trap MGO to generate the corresponding mono-MGO conjugates. Moreover, TF is oxidized to dehydrotheaflavin, which underwent further amination in the gut. By exposing TF to germ-free (GF) mice and conventionalized mice (GF mice colonized with specific-pathogen-free microbiota), the gut microbiota is demonstrated to facilitate the amination and MGO conjugation of TF. CONCLUSION: TF has the capacity to remove the endogenous metabolic toxins through oxidation, amination, and MGO conjugation in the intestinal tract, which can potentially explain why TF still generates in vivo efficacy while showing a poor systematic bioavailability.

Organic Cation Transporters in Human Physiology, Pharmacology, and Toxicology.

Individual cells and epithelia control the chemical exchange with the surrounding environment by the fine-tuned expression, localization, and function of an array of transmembrane proteins that dictate the selective permeability of the lipid bilayer to small molecules, as actual gatekeepers to the interface with the extracellular space. Among the variety of channels, transporters, and pumps that localize to cell membrane, organic cation transporters (OCTs) are considered to be extremely relevant in the transport across the plasma membrane of the majority of the endogenous substances and drugs that are positively charged near or at physiological pH. In humans, the following six organic cation transporters have been characterized in regards to their respective substrates, all belonging to the solute carrier 22 (SLC22) family: the organic cation transporters 1, 2, and 3 (OCT1-3); the organic cation/carnitine transporter novel 1 and 2 (OCTN1 and N2); and the organic cation transporter 6 (OCT6). OCTs are highly expressed on the plasma membrane of polarized epithelia, thus, playing a key role in intestinal absorption and renal reabsorption of nutrients (e.g., choline and carnitine), in the elimination of waste products (e.g., trimethylamine and trimethylamine N-oxide), and in the kinetic profile and therapeutic index of several drugs (e.g., metformin and platinum derivatives). As part of the Special Issue Physiology, Biochemistry, and Pharmacology of Transporters for Organic Cations, this article critically presents the physio-pathological, pharmacological, and toxicological roles of OCTs in the tissues in which they are primarily expressed.

Drug Delivery Strategies for Enhancing the Therapeutic Efficacy of Toxin-Derived Anti-Diabetic Peptides.

Toxin peptides derived from the skin secretions of amphibians possess unique hypoglycemic activities. Many of these peptides share cationic and amphipathic structural similarities and appear to possess cell-penetrating abilities. The mechanism of their insulinotropic action is yet not elucidated, but they have shown great potential in regulating the blood glucose levels in animal models. Therefore, they have emerged as potential drug candidates as therapeutics for type 2 diabetes. Despite their anti-diabetic activity, there remain pharmaceutical challenges to be addressed for their clinical applications. Here, we present an overview of recent studies related to the toxin-derived anti-diabetic peptides derived from the skin secretions of amphibians. In the latter part, we introduce the bottleneck challenges for their delivery in vivo and general drug delivery strategies that may be applicable to extend their blood circulation time. We focus our research on the strategies that have been successfully applied to improve the plasma half-life of exendin-4, a clinically available toxin-derived anti-diabetic peptide drug.

FRCD: A comprehensive food risk component database with molecular scaffold, chemical diversity, toxicity, and biodegradability analysis.

The presence of natural toxins, pesticide residues, and illegal additives in food products has been associated with a range of potential health hazards. However, no systematic database exists that comprehensively includes and integrates all research information on these compounds, and valuable information remains scattered across numerous databases and extensive literature reports. Thus, using natural language processing technology, we curated 12,018 food risk components from 152,737 literature reports, 12 authoritative databases, and numerous related regulatory documents. Data on molecular structures, physicochemical properties, chemical taxonomy, absorption, distribution, metabolism, excretion, toxicity properties, and physiological targets within the human body were integrated to afford the comprehensive food risk component database (FRCD, http://www.rxnfinder.org/frcd/). We also analyzed the molecular scaffold and chemical diversity, in addition to evaluating the toxicity and biodegradability of the food risk components. The FRCD could be considered a highly promising tool for future food safety studies.

Multiple Dose Pharmacokinetic Models Predict Bioavailability of Toxins in Vertebrate Herbivores.

In this paper, compartmental pharmacokinetic models are built to predict the concentration of toxic phytochemical in the gastrointestinal tract and blood following oral intake by an individual vertebrate herbivore. The existing single and multiple dose pharmacokinetic models are extended by inclusion of impulsive differential equations which account for an excretion factor whereby unchanged toxins are excreted in the feces due to gastrointestinal mobility. An index α is defined to measure the fraction of bioavailability attributed to the excretion factor of gastrointestinal motility. Sensitivity analysis was conducted and suggests, for any toxin, the bioavailability index α depends mostly on absorption rate of toxin from gastrointestinal tract into the blood, frequency of elimination due to gastrointestinal motility, and the frequency of toxin intake, under the model assumptions.

Multipoint dilution hemofiltration: A new technology for maximum convective clearance.

Convection-based renal replacement therapies (RRTs) have the potential to improve patient outcomes when compared to diffusion-based RRT such as hemodialysis (HD), but have limited clearance rates. We propose and characterize multipoint dilution hemofiltration (MPD-HF), a purely convective blood purification technology which removes the fundamental filtration limit associated with convective RRT resulting in clearance rates on par with HD. In MPD-HF, filtration of liquid and solutes occurs along the length of the hollow fibers that convey the blood, and substitution fluid is pushed into the fibers at multiple points along their length. Since multiple filtration and dilution steps are contained within one pass of the blood through the hollow fiber, the fraction of fluid that can be filtered may be increased to allow a high clearance rate that removes a wide range of toxins. In vitro tests yielded an average steady-state filtrate fraction of 68%, exceeding commercial HDF cartridge filtrate fractions by a factor of approximately 3. The molecular weights of molecules cleared spans up to the cutoff of 66 kDa for albumin.

Bioaccessibility of lipophilic and hydrophilic marine biotoxins in seafood: An in vitro digestion approach.

This study aimed to assess the bioaccessibility of different marine biotoxins in naturally contaminated shellfish and fish gonads using an in vitro digestion methodology. In general, hydrophilic toxins (domoic acid, paralytic shellfish poisoning toxins and tetrodotoxins) showed higher bioaccessibility than lipophilic ones (okadaic acid and azaspiracids). The bioaccessibility of toxins from the okadaic acid group ranged from 69% (raw European razor clams) to 74% (raw donax clams). Regarding azaspiracids, 47% of the initial content was bioaccessible in steamed blue mussel. As for hydrophilic toxins, 100% of the initial content was bioaccessible after digestion in raw shellfish and puffer fish gonads. The total tetrodotoxin bioaccessibility in puffer fish gonads decreased significantly after steaming. The profile of tetrodotoxins changed during the digestion process: TTX and 11-norTTX-6S-ol analogues decreased significantly after digestion, but the 5,6,11-trideoxy TTX analogue increased in both raw and steamed puffer fish gonads. These preliminary findings confirm the need to consider bioaccessibility data in future seafood risk assessment, as such information enables a more accurate and realistic estimation of potential seafood hazards, particularly in what concerns lipophilic toxins, therefore, constituting a crucial tool in the refinement of regulatory limits for the presence of biotoxins in seafood.

Pharmacokinetics of Toxin-Derived Peptide Drugs.

Toxins and venoms produced by different organisms contain peptides that have evolved to have highly selective and potent pharmacological effects on specific targets for protection and predation. Several toxin-derived peptides have become drugs and are used for the management of diabetes, hypertension, chronic pain, and other medical conditions. Despite the similarity in their composition (amino acids as the building blocks), toxin-derived peptide drugs have very profound differences in their structure and conformation, in their physicochemical properties (that affect solubility, stability, etc.), and subsequently in their pharmacokinetics (the processes of absorption, distribution, metabolism, and elimination following their administration to patients). This review summarizes and critically analyzes the pharmacokinetic properties of toxin-derived peptide drugs: (1) the relationship between the chemical structure, physicochemical properties, and the pharmacokinetics of the specific drugs, (2) the major pharmacokinetic properties and parameters of these drugs, and (3) the major pharmacokinetic variability factors of the individual drugs. The structural properties of toxin-derived peptides affect their pharmacokinetics and pose some limitations on their clinical use. These properties should be taken into account during the development of new toxin-derived peptide drugs, and for the efficient and safe use of the clinically approved drugs from this group in the individual patients.

Detoxifying symbiosis: microbe-mediated detoxification of phytotoxins and pesticides in insects.

Covering: up to 2018 Insects live in a world full of toxic compounds such as plant toxins and manmade pesticides. To overcome the effects of these toxins, herbivorous insects have evolved diverse, elaborate mechanisms of resistance, such as toxin avoidance, target-site alteration, and detoxification. These resistance mechanisms are thought to be encoded by the insects' own genomes, and in many cases, this holds true. However, recent omics analyses, in conjunction with classic culture-dependent analyses, have revealed that a number of insects possess specific gut microorganisms, some of which significantly contribute to resistance against phytotoxins and pesticides by degrading such chemical compounds. Here, we review recent advances in our understanding on the symbiont-mediated degradation of natural and artificial toxins, with a special emphasis on their underlying genetic basis, focus on the importance of environmental microbiota as a resource of toxin-degrading microorganisms, and discuss the ecological and evolutionary significance of these symbiotic associations.

Elimination of a Viscumin-Ferromagnetic Nanoparticles Conjugate from the Tumor Nodule in Mice.

External magnetic field is characterized by low toxicity and existence of magnetic properties, which contributes to an interest in the development of products from ferromagnetic nanoparticles (FNP) for antitumor therapy. Previously we synthesized a conjugate of ferromagnetic magnetite nanoparticles and viscumin (mistletoe lectin I, MLI), which exhibits the antitumor activity. Studying the pharmacological properties of this conjugate (FNP-MLI) was directed to the evaluation of FNP-MLI elimination after intratumor injection in mice. The elimination rate of FNP-MLI was much lower than that of native plant MLI. The presence of FNP-MLI was not accompanied by undesired changes in the tumor tissue. The use of a FNP-MLI conjugate allowed us to prolong the time of MLI presence in tissues without increasing the dose of exogenous lectin. These features contribute to the prolongation of an immunomodulatory effect of MLI.

Biodistribution of Viscumin after Subcutaneous Injection to Mice and In Vitro Modeling of Endoplasmic Reticulum Stress.

Viscumin (mistletoe lectin I, MLI) in concentrations of 10-11-10-7 M causes endoplasmic reticulum stress and triggers unfolded protein response, a modulator of antitumor immunity, in target cells.

Comparison of the serum toxicokinetics of larkspur toxins in cattle, sheep and goats.

Larkspurs (Delphinium spp.) are a major cause of cattle losses in western North America, whereas sheep are thought to be resistant to larkspur toxicosis. Goats are often used as a small ruminant model to study poisonous plants. In this study, we compared the serum toxicokinetic profile of toxic larkspur alkaloids from Delphinium barbeyi in cattle, goats, and sheep. The results from this study indicate that kinetic differences could partially explain species differences in susceptibility to larkspur toxicosis.

Toxin effect on protein biosynthesis in eukaryotic cells: a simple kinetic model.

A model for toxin inhibition of protein synthesis inside eukaryotic cells is presented. Mitigation of this effect by introduction of an antibody is also studied. Antibody and toxin (ricin) initially are delivered outside the cell. The model describes toxin internalization from the extracellular into the intracellular domain, its transport to the endoplasmic reticulum (ER) and the cleavage inside the ER into the RTA and RTB chains, the release of RTA into the cytosol, inactivation (depurination) of ribosomes, and the effect on translation. The model consists of a set of ODEs which are solved numerically. Numerical results are illustrated by figures and discussed.

Removal of Different Classes of Uremic Toxins in APD vs CAPD: A Randomized Cross-Over Study.

UNLABELLED: ♦ AIM: In this study, we investigated, and this for the different classes of uremic toxins, whether increasing dialysate volume by shifting from continuous ambulatory peritoneal dialysis (CAPD) to higher volume automated peritoneal dialysis (APD) increases total solute clearance. ♦ METHODS: Patients on peritoneal dialysis were randomized in a cross-over design to one 24-hour session of first a CAPD regimen (3*2 L of Physioneal 1.36% and 1*2 L of icodextrin) or APD (consisting of 5 cycles of 2 L Physioneal 1.36 and 1 cycle of 2 L Extraneal), and the other week the alternate regime, each patient serving as his/her own control. Dialysate, blood and urine samples were collected and frozen for later batch analysis of concentrations of urea, creatinine, phosphorus, uric acid, hippuric acid, 3-carboxy-4-methyl-5-propyl-2-furanpropionic acid, indoxyl sulfate, indole acetic acid, and p-cresyl sulfate. For the protein-bound solutes, total and free fractions were determined. Total, peritoneal and renal clearance (K) and mass removal (MR) of each solute were calculated, using validated models. ♦ RESULTS: In 15 patients (11 male, 3 diabetics, 56 ± 16 years, 8 on CAPD, time on peritoneal dialysis 12 ± 14 months, and residual renal function of 9.9 ± 5.4 mL/min) dialysate over plasma ratio for creatinine (D/Pcrea) was 0.62 ± 0.10. Drained volume and obtained ultrafiltration were higher with APD vs CAPD (13.3 ± 0.5 L vs 8.5 ± 0.7 L and 1.3 ± 0.5 L vs 0.5 ± 0.7 L), whereas urine output was lower (1.0 ± 0.5 L vs 1.4 ± 0.6 L). Total clearance and MR tended to be higher for CAPD vs APD for all small and water soluble solutes, but mainly because of higher renal contribution, with no difference in the peritoneal contribution. For the protein-bound solutes, no differences in clearance or mass removal were observed. ♦ CONCLUSION: Although the drained dialysate volume nearly doubled, APD did not result in better peritoneal clearance or solute removal vs classic CAPD. APD resulted in better ultrafiltration, but at the expense of residual urinary output and clearance.

Deoxynivalenol in the gastrointestinal tract of immature gilts under per os toxin application.

Deoxynivalenol is also known as vomitoxin due to its impact on livestock through interference with animal growth and acceptance of feed. At the molecular level, deoxynivalenol disrupts normal cell function by inhibiting protein synthesis via binding to the ribosome and by activating critical cellular kinases involved in signal transduction related to proliferation, differentiation and apoptosis. Because of concerns related to deoxynivalenol, the United States FDA has instituted advisory levels of 5 µg/g for grain products for most animal feeds and 10 µg/g for grain products for cattle feed. The aim of the study was to determine the effect of low doses of deoxynivalenol applied per os on the presence of this mycotoxin in selected tissues of the alimentary canal of gilts. The study was performed on 39 animals divided into two groups (control, C; n = 21 and experimental, E; n = 18), of 20 kg body weight at the beginning of the experiment. Gilts received the toxin in doses of 12 µg/kg b.w./day (experimental group) or placebo (control group) over a period of 42 days. Three animals from two experimental groups were sacrificed on days 1, 7, 14, 21, 28, 35 and 42, excluding day 1 when only three control group animals were scarified. Tissues samples were prepared for high performance liquid chromatography (HPLC) analyses with the application of solid phase extraction (SPE). The results show that deoxynivalenol doses used in our study, even when applied for a short period, resulted in its presence in gastrointestinal tissues. The highest concentrations of deoxynivalenol reported in small intestine samples ranged from 7.2 (in the duodenum) to 18.6 ng/g (in the ileum) and in large intestine samples from 1.8 (in transverse the colon) to 23.0 ng/g (in the caecum). In liver tissues, the deoxynivalenol contents ranged from 6.7 to 8.8 ng/g.

Generation and characterization of a Cyp4b1 null mouse and the role of CYP4B1 in the activation and toxicity of Ipomeanol.

4-Ipomeanol (IPO) is a prototypical pulmonary toxin that requires P450-mediated metabolic activation to reactive intermediates in order to elicit its toxic effects. CYP4B1 is a pulmonary enzyme that has been shown, in vitro, to have a high capacity for bioactivating IPO. In order to determine, unambiguously, the role of CYP4B1 in IPO bioactivation in vivo, we generated Cyp4b1 null mice following targeted disruption of the gene downstream of exon 1. Cyp4b1 (-/-) mice are viable and healthy, with no overt phenotype, and no evidence of compensatory upregulation of other P450 isoforms in any of the tissues examined. Pulmonary and renal microsomes prepared from male Cyp4b1 (-/-) mice exhibited no detectable expression of the protein and catalyzed the in vitro bioactivation of IPO at < 10% of the rates observed in tissue microsomes from Cyp4b1 (+/+) animals. Administration of IPO (20mg/kg) to Cyp4b1 (+/+) mice resulted in characteristic lesions in the lung, and to a lesser extent in the kidney, which were completely absent in Cyp4b1 (-/-) mice. We conclude that CYP4B1 is a critical enzyme for the bioactivation of IPO in vivo and that the Cyp4b1 (-/-) mouse is a useful model for studying CYP4B1-dependent metabolism and toxicity.

A pharm-ecological perspective of terrestrial and aquatic plant-herbivore interactions.

We describe some recent themes in the nutritional and chemical ecology of herbivores and the importance of a broad pharmacological view of plant nutrients and chemical defenses that we integrate as "Pharm-ecology". The central role that dose, concentration, and response to plant components (nutrients and secondary metabolites) play in herbivore foraging behavior argues for broader application of approaches derived from pharmacology to both terrestrial and aquatic plant-herbivore systems. We describe how concepts of pharmacokinetics and pharmacodynamics are used to better understand the foraging phenotype of herbivores relative to nutrient and secondary metabolites in food. Implementing these concepts into the field remains a challenge, but new modeling approaches that emphasize tradeoffs and the properties of individual animals show promise. Throughout, we highlight similarities and differences between the historic and future applications of pharm-ecological concepts in understanding the ecology and evolution of terrestrial and aquatic interactions between herbivores and plants. We offer several pharm-ecology related questions and hypotheses that could strengthen our understanding of the nutritional and chemical factors that modulate foraging behavior of herbivores across terrestrial and aquatic systems.

High correlation between clearance of renal protein-bound uremic toxins (indoxyl sulfate and p-cresyl sulfate) and renal water-soluble toxins in peritoneal dialysis patients.

Peritoneal dialysis (PD) is characterized by a slow continuous removal of solutes. Traditionally, dialysis adequacy is quantified by referring to the kinetics of urea nitrogen (UN) and creatinine (Cr) clearance. The efficacy of middle molecular substances and protein-bound solutes as markers for peritoneal dialysis adequacy is not clear. The aim of this cross-sectional study was to investigate correlations between the clearance of indoxyl sulfate (IS), p-cresyl sulfate (PCS), UN, and Cr in the peritoneum and kidneys and to compare the overall clearances of IS and PCS between non-anuric and anuric groups in PD patients. We recruited a total of 175 patients who had been undergoing continuous ambulatory PD (CAPD) or automated PD (APD) for at least 4 months. We measured total IS and PCS concentrations in serum, dialysate, and urine samples. Free IS and PCS concentrations were measured in all serum samples. IS and PCS clearances via both kidney and peritoneum were measured. The mean concentration of IS in the urine samples was 9.2-fold higher than that in the dialysate samples, and concentration of PCS in the urine samples was 8.5-fold higher than that in the dialysate samples. Peritoneal UN and Cr clearances were not correlated with peritoneal PCS clearance (P > 0.05) but were mildly correlated with peritoneal IS clearance. The peritoneal IS and PCS clearances in the different peritoneal equilibration test groups were similar. The renal UN and Cr clearances were strongly correlated with renal PCS and IS clearances (P > 0.89, P < 0.001). In addition, non-anuric patients showed better elimination of total PCS (10.3 mg/day [range, 1.6-19.8] vs. 5.2 mg/day [range, 0-14]; P < 0.001] and IS (37.9 mg/day [range, 25.6-56.7] vs. 24.8 mg/day [range, 17.1-41.6]; P < 0.001) than anuric patients. This cross-sectional study showed that peritoneal clearance of water-soluble solutes is not correlated with that of PCS but is mildly correlated with that of IS. However, the renal clearances of IS and PCS show strong positive correlation with the renal clearances of UN and Cr. This study confirms the important role of residual renal function in the removal of protein-bound uremic toxins.

Adapting yeast as model to study ricin toxin a uptake and trafficking.

The plant A/B toxin ricin represents a heterodimeric glycoprotein belonging to the family of ribosome inactivating proteins, RIPs. Its toxicity towards eukaryotic cells results from the depurination of 28S rRNA due to the N-glycosidic activity of ricin toxin A chain, RTA. Since the extention of RTA by a mammalian-specific endoplasmic reticulum (ER) retention signal (KDEL) significantly increases RTA in vivo toxicity against mammalian cells, we here analyzed the phenotypic effect of RTA carrying the yeast-specific ER retention motif HDEL. Interestingly, such a toxin (RTA(HDEL)) showed a similar cytotoxic effect on yeast as a corresponding RTA(KDEL) variant on HeLa cells. Furthermore, we established a powerful yeast bioassay for RTA in vivo uptake and trafficking which is based on the measurement of dissolved oxygen in toxin-treated spheroplast cultures of S. cerevisiae. We show that yeast spheroplasts are highly sensitive against external applied RTA and further demonstrate that its toxicity is greatly enhanced by replacing the C-terminal KDEL motif by HDEL. Based on the RTA resistant phenotype seen in yeast knock-out mutants defective in early steps of endocytosis (∆end3) and/or in RTA depurination activity on 28S rRNA (∆rpl12B) we feel that the yeast-based bioassay described in this study is a powerful tool to dissect intracellular A/B toxin transport from the plasma membrane through the endosomal compartment to the ER.