Identification of novel metabolites of colchicine in rat bile facilitated by enhanced online radiometric detection

A new insight into mechanism of colchicine poisoning based on untargeted metabolomics

BACKGROUND

Colchicine (COL) is a well-known plant-derived mitogenic toxin that has been widely applied for the treatment of immune system diseases and various cancers. However, its clinical use is severely limited by frequent occurrence of poisoning accidents, and the mechanism of COL poisoning is not clear yet.

PURPOSE

The present study aimed to unveil how COL works as a toxin based on untargeted metabolomics analysis of animal models and clinical human case.

METHODS

KM mice orally administered COL were used to establish poisoning models, and plasma samples were collected for untargeted metabolomics analysis. The data mining was performed to screen dose-dependent differences and disturbed metabolic pathways. The blood samples collected from clinical COL poisoning human case at various time points during treatment period were further analyzed to investigate the temporal changes in the metabolic disposition of COL in vivo and also verify the findings from mice. Finally, the expression of key pathways was evaluated by ELISA and Western blotting analysis.

RESULTS

Histological examination demonstrated systemic toxicity of COL poisoning in mice. Metabolite profiling analysis of plasma samples from model mice and clinical case both revealed that COL poisoning could significantly disturb in vivo metabolism of amino acid and lipid metabolism by the FXR/AMPK signal pathway. Quantitative monitoring of the metabolic process of COL further demonstrated that it could be greatly ameliorated with the rapid metabolic transformation of COL in vivo, which thus may be an effective detoxification pathway for COL poisoning.

CONCLUSION

The findings of the present study provided new insight into the molecular mechanism of COL poisoning, thus helpful for guiding reasonable application of this phytotoxin.

A New Insight into Toxicity of Colchicine Analogues by Molecular Docking Analysis Based on Intestinal Tight Junction Protein ZO-1

Colchicine (COL) is a well-known plant alkaloid long used for medical purposes due to the selective anti-inflammatory effect on acute gouty arthritis. It is also a kind of mitosis toxin with strong inhibitory effects of cell division and is therefore being applied to the treatment of various cancers. However, this product shows a variety of adverse effects that are significantly correlated with the dosage and have attracted much attention. For the first time, the present work obtained a new insight into the gastrointestinal toxicity of colchicine analogues by molecular docking analysis, which was based on the 3D structure of intestinal tight junction protein ZO-1 and the ligand library containing dozens of small-molecule compounds with the basic skeleton of COL and its metabolites. The binding energy and mode of protein–ligand interaction were investigated to better understand the structure–toxicity relationships of COL analogues and the mechanism of action as well. Cluster analysis clearly demonstrated the strong correlation between the binding energy and toxicity of ligand molecules. The interaction mode further revealed that the hydrogen bonding (via the C-7 amide or C-9 carbonyl group) and hydrophobic effect (at ring A or C) were both responsible for ZO-1-related gastrointestinal toxicity of COL analogues, while metabolic transformation via phase I and/or phase II reaction would significantly attenuate the gastrointestinal toxicity of colchicine, indicating an effective detoxication pathway through metabolism.

Isolation and Structure Elucidation of Glucosylated Colchicinoids from the Seeds of Gloriosa superba by LC-DAD-SPE-NMR

Four new colchicinoids were isolated from the seeds of Gloriosa superba together with the known compounds colchicoside (4) and 3-de-O-methylcolchicine-3-O-β-d-glucopyranosyl-(1→4)-3-O-β-d-glucopyranoside (6), by means of conventional column chromatography and LC-DAD-SPE-NMR. The new compounds were identified as N-deacetyl-N-formyl-3-de-O-methylcolchicine-3-O-β-d-glucopyranoside (1), 3-de-O-methylcolchicine-3-O-β-d-glucopyranosyl-(1→6)-3-O-β-d-glucopyranoside (2), N-deacetyl-N-formyl-3-de-O-methylcolchicine-3-O-β-d-glucopyranosyl-(1→6)-3-O-β-d-glucopyranoside (3), and 3-de-O-methylcolchicine-3-O-β-d-glucopyranosyl-(1→3)-3-O-β-d-glucopyranoside (5). The structure elucidation was performed by means of NMR (COSY, HSQC, and HMBC), HRESIMS/MS, and GCMS data analysis.

Electrophilicities and Protein Covalent Binding of Demethylation Metabolites of Colchicine

Colchicine, an alkaloid existing in plants of Liliaceous colchicum, has been widely used in the treatment of gout and familial Mediterranean fever. The administration of colchicine was found to cause liver injury in humans. The mechanisms of colchicine-induced liver toxicity remain unknown. The objectives of this study were to determine the electrophilicities of demethylation metabolites of colchicine and investigate the protein adductions derived from the reactive metabolites of colchicine. Four demethylated colchicine (1-, 2-, 3-, and 10-DMCs), namely, M1-M4, were detected in colchicine-fortified microsomal incubations. Four N-acetyl cysteine (NAC) conjugates (M5-M8) derived from colchicine were detected in the microsomes in the presence of NAC. M5 and M6 were derived from 10-DMC. M7 resulted from the reaction of 2-DMC or 3-DMC with NAC, and M8 originated from 10-DMC. Microsomal protein covalent binding was observed after exposure to colchicine. Two cysteine adducts (CA-1 and CA-2) derived from 10-DMC were found in proteolytically digested microsomal protein samples after incubation with colchicine. The findings allow us to define the chemical property of demethylation metabolites of colchicine and the interaction between protein and the reactive metabolites of colchicine generated in situ.

Development and application of purified tissue dissociation enzyme mixtures for human hepatocyte isolation

Human hepatocyte transplantation is gaining acceptance for the treatment of liver diseases. However, the reagents used to isolate hepatocytes from liver tissue are not standardized and show lot-to-lot variability in enzyme activity and endotoxin contamination. For clinical application, highly purified reagents are preferable to crude digest preparations. A purified tissue dissociating enzyme (TDE) preparation (CIzyme(TM) purified enzymes) was developed based on the enzyme compositions found in a superior lot of collagenase previously used by our group for human hepatocyte isolation. The performance of this enzyme preparation was compared to collagenase type XI on 110 liver cases by assessing hepatocyte yield, viability, and seven other functional assays that included plating efficiency, basal and induced CYP450 activities, phase II conjugation activity, and ammonia metabolism. No statistically significant difference was observed between these TDEs when they were used to isolate hepatocytes from liver resections or organ donor tissue on 54 hepatocyte isolations with type XI enzyme and 56 isolations using CIzyme(TM). These results show that a highly purified and defined TDE preparation can be formulated that provides excellent performance with respect to viability, yield, and functional activity of the isolated cells. In addition to reproducible formulation, these purified enzyme products have only 2-3% of the endotoxin of crude enzyme preparations. These results show that purified enzymes such as CIzyme(TM) will be a safe and effective for the isolation of human hepatocytes for clinical transplants.

Hepatobiliary toxicity of furan: identification of furan metabolites in bile of male f344/n rats

Furan, which occurs in a wide variety of heat-treated foods, is a potent hepatotoxicant and liver carcinogen in rodents. In a 2-year bioassay, furan caused hepatocellular adenomas and carcinomas in mice and rats but also high incidences of bile duct tumors in rats. Furan is bioactivated by cytochrome P450 enzymes to cis-2-butene-1,4-dial, an α,β-unsaturated dialdehyde, which readily reacts with tissue nucleophiles. The objective of this study was to structurally characterize furan metabolites excreted with bile to better understand the potential role of reactive furan intermediates in the biliary toxicity of furan. Bile duct-cannulated F344/N rats (n = 3) were administered a single oral dose of 5 mg/kg b.wt. [(12)C(4)]furan or stable isotope-labeled [3,4-(13)C]furan, and bile samples collected at 30-min intervals for 4 h were analyzed by liquid chromatography-tandem mass spectrometry. A total of eight furan metabolites derived from reaction of cis-2-butene-1,4-dial with GSH and/or amino acids and subsequent enzymatic degradation were detected in bile. The main metabolite was a cyclic monoglutathione conjugate of cis-2-butene-1,4-dial, which was previously detected in urine of furan-treated rats. Furthermore, a N-acetylcysteine-N-acetyllysine conjugate, previously observed in rat urine, and a cysteinylglycine-glutathione conjugate were identified as major metabolites. These data suggest that degraded protein adducts are in vivo metabolites of furan, consistent with the hypothesis that cytotoxicity mediated through binding of cis-2-butene-1,4-dial to critical target proteins is likely to play a key role in furan toxicity and carcinogenicity.

A Fatal Case of Autumn Crocus (Colchicum Autumnale) Poisoning in a Heifer: Confirmation by Mass-Spectrometric Colchicine Detection

A heifer developed severe signs of acute gastrointestinal irritation 48 hr after ingesting fresh leaves of Colchicum autumnale growing on a damp meadow. Confirmation of the suspected toxicosis was obtained by detecting colchicine in serum and urine using liquid chromatography coupled with tandem mass spectrometry using atmospheric pressure chemical ionization. Although the serum colchicine concentration had declined to an apparently nontoxic level of 2.4 ng/ml, a more prominent concentration (640 ng/ml) indicative of colchicine poisoning was detected in the urine. This finding is consistent with the known toxicokinetic properties of colchicine, whereby a large volume of distribution results in low circulating blood concentrations and prolonged urinary excretion.