Pharmacokinetics of α-amanitin in mice using liquid chromatography-high resolution mass spectrometry and in vitro drug-drug interaction potentials

Toxicokinetics of α- and β-amanitin in mice following single and combined administrations: Simulating in vivo amatoxins processes in clinical cases

α-Amanitin and β-amanitin, two of the most toxic amatoxin compounds, typically coexist in the majority of Amanita mushrooms. The aim of this study was to use a newly developed ultra-performance liquid chromatography-mass spectrometry (UPLC-MS/MS) method to determine the toxicokinetics and tissue distribution of α- and β-amanitin following single or combined oral (po) administration in mice. α-Amanitin and β-amanitin administered at 2 or 10 mg/kg doses showed similar toxicokinetic profiles, except for peak concentration (Cmax). The elimination half-life (t1/2) values of α-amanitin and β-amanitin in mice were 2.4-2.8 h and 2.5-2.7 h, respectively. Both α- and β-amanitin were rapidly absorbed into the body, with times to reach peak concentration (Tmax) between 1.0 and 1.5 h. Following single oral administration at 10 mg/kg, the Cmax was significantly lower for α-amanitin (91.1 μg/L) than for β-amanitin (143.1 μg/L) (p < 0.05). The toxicokinetic parameters of α-amanitin, such as t1/2, mean residence time (MRT), and volume of distribution (Vz/F) and of β-amanitin, such as Vz/F, were significantly different (p < 0.05) when combined administration was compared to single administration. Tissues collected at 24 h after po administration revealed decreasing tissue distributions for α- and β-amanitin of intestine > stomach > kidney > lung > spleen > liver > heart. The substantial distribution of toxins in the kidney corresponds to the known target organs of amatoxin poisoning. The content in the stomach, liver, and kidney was significantly higher for of β-amanitin than for α-amanitin at 24 h following oral administration of a 10 mg/kg dose. No significant difference was detected in the tissue distribution of either amatoxin following single or combined administration. After po administration, both amatoxins were primarily excreted through the feces. Our data suggest the possibility of differences in the toxicokinetics in patients poisoned by mushrooms containing both α- and β-amanitin than containing a single amatoxin. Continuous monitoring of toxin concentrations in patients' blood and urine samples is necessary in clinical practice.

Amanitin-induced variable cytotoxicity in various cell lines is mediated by the different expression levels of OATP1B3

Amanita phalloides is one of the deadliest mushrooms worldwide, causing most fatal cases of mushroom poisoning. Among the poisonous substances of Amanita phalloides, amanitins are the most lethal toxins to humans. Currently, there are no specific antidotes available for managing amanitin poisoning and treatments are lack of efficacy. Amanitin mainly causes severe injuries to specific organs, such as the liver, stomach, and kidney, whereas the lung, heart, and brain are hardly affected. However, the molecular mechanism of this phenomenon remains not understood. To explore the possible mechanism of organ specificity of amanitin-induced toxicity, eight human cell lines derived from different organs were exposed to α, β, and γ-amanitin at concentrations ranging from 0.3 to 100 μM. We found that the cytotoxicity of amanitin differs greatly in various cell lines, among which liver-derived HepG2, stomach-derived BGC-823, and kidney-derived HEK-293 cells are most sensitive. Further mechanistic study revealed that the variable cytotoxicity is mainly dependent on the different expression levels of the organic anion transporting polypeptide 1B3 (OATP1B3), which facilitates the internalization of amanitin into cells. Besides, knockdown of OATP1B3 in HepG2 cells prevented α-amanitin-induced cytotoxicity. These results indicated that OATP1B3 may be a crucial therapeutic target against amanitin-induced organ failure.

What is the role of current mass spectrometry in pharmaceutical analysis?

The role of mass spectrometry (MS) has become more important in most application domains in recent years. Pharmaceutical analysis is specific due to its stringent regulation procedures, the need for good laboratory/manufacturing practices, and a large number of routine quality control analyses to be carried out. The role of MS is, therefore, very different throughout the whole drug development cycle. While it dominates within the drug discovery and development phase, in routine quality control, the role of MS is minor and indispensable only for selected applications. Moreover, its role is very different in the case of analysis of small molecule pharmaceuticals and biopharmaceuticals. Our review explains the role of current MS in the analysis of both small-molecule chemical drugs and biopharmaceuticals. Important features of MS-based technologies being implemented, method requirements, and related challenges are discussed. The differences in analytical procedures for small molecule pharmaceuticals and biopharmaceuticals are pointed out. While a single method or a small set of methods is usually sufficient for quality control in the case of small molecule pharmaceuticals and MS is often not indispensable, a large panel of methods including extensive use of MS must be used for quality control of biopharmaceuticals. Finally, expected development and future trends are outlined.

Biodistribution of radiolabeled alpha-amanitin in mice: An Investigation

Mushroom poisonings caused by Amanita phalloides are the leading cause of mushroom-related deaths worldwide. Alpha-Amanitin (α-AMA), a toxic substance present in these mushrooms, is responsible for the resulting hepatotoxicity and nephrotoxicity. The objective of our study was to determine the distribution of α-AMA in Balb/c mice by labeling with Iodine-131. Mice were injected with a toxic dose (1.4 mg/kg) of α-AMA labeled with Iodine-131. The mice were sacrificed at the 1st, 2nd, 4th, 8th, 24th, and 48th hours under anesthesia. The organs of the mice were removed, and their biodistribution was assessed in all experiments. The percent injected dose per gram (ID/g %) value for kidney, liver, lung, and heart tissues at 1st hour were 1.59 ± 0.07, 1.25 ± 0.33, 3.67 ± 0.80 and 1.07 ± 0.01 respectively. This study provides insights into the potential long-term effects of α-AMA accumulation in specific organs. Additionally, this study has generated essential data that can be used to demonstrate the impact of antidotes on the biological distribution of α-AMA in future toxicity models.

Acute hepatic and kidney injury after ingestion of Lepiota brunneoincarnata: Report of 2 cases

Lepiota brunneoincarnata is a highly toxic mushroom species known to cause acute liver failure. However, there are limited reports investigating L. brunneoincarnata causing acute hepatic and renal damage. The present article reports 2 cases of L. brunneoincarnata poisoning in a mother and son from Chuxiong City, Yunnan Province, China. Both patients presented with gastrointestinal symptoms approximately 8-9 h after ingesting the suspect mushrooms and sought medical attention 27-28 h post-ingestion, both exhibiting acute hepatic and kidney injuries. Morphological and molecular biology studies confirmed the species of the mushrooms as L. brunneoincarnata. Liquid chromatography-tandem mass spectrometry analysis revealed mean fresh-weight concentrations of 123.5 μg/g α-amanitin and 45.7 μg/g β-amanitin in the mushrooms. The patients underwent standard treatments, including multiple-dose activated charcoal, oral silibinin capsules, N-acetylcysteine, penicillin G, hemoperfusion, and plasma exchange. One patient recovered completely and was discharged after 16 days of hospitalization. The other patient exhibited gradual improvement in liver and renal function; however, renal function deteriorated 9 days after ingestion, and the patient declined renal replacement therapy and returned home 14 days post-ingestion. The patient was then re-hospitalized due to oliguria and edema in both lower extremities. Renal biopsy revealed acute tubular necrosis, inflammatory cell infiltration, minor glomerular capsular fibrosis, loss of microvilli in the renal tubular epithelial cells, and interstitial edema. The patient underwent 2 rounds of continuous renal replacement therapy, which eventually resulted in improvement, and was discharged 31 days after mushroom consumption. It is noteworthy that this patient had already progressed to chronic kidney insufficiency 11 months after intoxication.

Simple and rapid detection of three amatoxins and three phallotoxins in human body fluids by UPLC-MS-MS and its application in 15 poisoning cases

Amatoxins and phallotoxins are toxic cyclopeptides found in the genus Amanita and are among the predominant causes of foodborne sickness and poisoning-related fatalities in China. This study introduces and validates a simple, rapid and cost-effective ultra-performance liquid chromatography-mass spectrometry method for the simultaneous determination and quantification of α-amanitin, β-amanitin, γ-amanitin, phallisacin, phallacidin and phalloidin in human blood and urine. Quick therapeutic decision-making is supported by a 9 min chromatographic separation performed on a Waters Acquity UPLC HSS T3 column (100 mm × 2.1 mm, 1.8 µm) using a gradient of high-performance liquid chromatography (HPLC)-grade water and methanol:0.005% formic acid. The analyte limit of quantification was 1-3 ng/mL in blood and 0.5-2 ng/mL in urine. Calibrations curves, prepared by spiking drug-free blood and urine, demonstrated acceptable linearity with mean correlation coefficients (r) greater than 0.99 for all phallotoxins and amatoxins. Acceptable intraday and interday precision (relative standard deviation <15%) and accuracy (bias, -4.8% to 13.0% for blood and-9.0% to 14.7% for urine) were achieved. The validated method was successfully applied to analyze 9 blood samples and 2 urine samples testing positive for amatoxins and/or phallotoxins. Amatoxins and/or phallotoxins were identified in each whole blood sample at a range of 1.12-5.63 ng/mL and in two urine samples from 1.01-9.27 ng/mL. The method has the benefits of simple sample preparation (protein precipitation) and wide analyte coverage, making it suitable for emergency quantitative surveillance toxicological analysis in clinics and forensic poisoning practice.

Identification of α-amanitin effector proteins in hepatocytes by limited proteolysis-coupled mass spectrometry

The misuse of poisonous mushrooms containing amatoxins causes acute liver failure (ALF) in patients and is a cause of significant mortality. Although the toxic mechanisms of α-amanitin (α-AMA) and its interactions with RNA polymerase II (RNAP II) have been studied, α-AMA effector proteins that can interact with α-AMA in hepatocytes have not been systematically studied. Limited proteolysis-coupled mass spectrometry (LiP-MS) is an advanced technology that can quickly identify protein-ligand interactions based on global comparative proteomics. This study identified the α-AMA effector proteins found in human hepatocytes, following the detection of conformotypic peptides using LiP-MS coupled with tandem mass tag (TMT) technology. Proteins that are classified into protein processing in the endoplasmic reticulum and the ribosome during the KEGG pathway can be identified through affinity evaluation, according to α-AMA concentration-dependent LiP-MS and LiP-MS in hepatocytes derived from humans and mice, respectively. The possibility of interaction between α-AMA and proteins containing conformotypic peptides was evaluated through molecular docking studies. The results of this study suggest a novel path for α-AMA to induce hepatotoxicity through interactions with various proteins involved in protein synthesis, as well as with RNAP II.

Toxicokinetics and tissue distribution of phalloidin in mice

Phalloidin, a bicyclic heptapeptide found in Amanita mushroom, specifically binds to F-actin in the liver causing cholestatic hepatotoxicity. However, the toxicokinetics and tissue distribution properties of phalloidin as well as their underlying mechanisms have to be studied further. The area under the plasma concentration curve (AUC) of phalloidin increased in proportion to the doses (0.2, 0.4, and 0.8 mg/kg for intravenous injection and 2, 5, and 10 mg/kg for oral administration). Phalloidin exhibited dose-independent low volume of distribution (395.6-456.9 mL/kg) and clearance (21.4-25.5 mL/min/kg) and low oral bioavailability (2.4%-3.3%). This could be supported with its low absorptive permeability (0.23 ± 0.05 × 10-6 cm/s) in Caco-2 cells. The tissue-to-plasma AUC ratios of intravenously injected and orally administered phalloidin were the highest in the liver and intestines, respectively, and also high in the kidneys, suggesting that the liver, kidneys, and intestines could be susceptible to phalloidin exposure and that active transport via the hepatic and renal organic anion transporters (OATP1B1, OATP1B3, and OAT3) may contribute to the higher distribution of phalloidin in the liver and kidneys.

Analytical methods for amatoxins: A comprehensive review

Amatoxins are toxic bicyclic octapeptides found in certain wild mushroom species, particularly Amanita phalloides. These mushrooms contain predominantly α- and β-amanitin, which can lead to severe health risks for humans and animals if ingested. Rapid and accurate identification of these toxins in mushroom and biological samples is crucial for diagnosing and treating mushroom poisoning. Analytical methods for the determination of amatoxins are critical to ensure food safety and prompt medical treatment. This review provides a comprehensive overview of the research literature on the determination of amatoxins in clinical specimens, biological and mushroom samples. We discuss the physicochemical properties of toxins, highlighting their influence on the choice of the analytical method and the importance of sample preparation, particularly solid-phase extraction with cartridges. Chromatographic methods are emphasised with a focus on liquid chromatography coupled to mass spectrometry as one of the most relevant analytical method for the determination of amatoxins in complex matrices. Furthermore, current trends and future perspectives in amatoxin detection are also suggested.

Determination of protein-bound α-amanitin in mouse plasma: A potential new indicator of poisoning with the mushroom toxin α-amanitin

Approximately 70%∼90% of mushroom poisoning deaths are caused by the class of mushroom toxins known as amatoxins. However, the rapid elimination of amatoxins from plasma within 48 h after mushroom ingestion limits the practical value of plasma amatoxin analysis as a diagnostic indicator of Amanita mushroom poisoning. To increase the positive detection rate and extend the detection window of amatoxin poisoning, we developed a new method to detect protein-bound α-amanitin based on the hypothesis that RNAP II-bound α-amanitin released from the tissue into the plasma could be degraded by trypsin hydrolysis and then detected by conventional liquid chromatography-mass spectrometry (LC‒MS). Toxicokinetic studies on mice intraperitoneally injected with 0.33 mg/kg α-amanitin were conducted to obtain and compare the concentration trends, detection rates, and detection windows of both free α-amanitin and protein-bound α-amanitin. By comparing detection results with and without trypsin hydrolysis in the liver and plasma of α-amanitin-poisoned mice, we verified the credibility of this method and the existence of protein-bound α-amanitin in plasma. Under the optimized trypsin hydrolysis conditions, we obtained a time-dependent trend of protein-bound α-amanitin in mouse plasma at 1-12 days postexposure. In contrast to the short detection window (0-4 h) of free α-amanitin in mouse plasma, the detection window of protein-bound α-amanitin was extended to 10 days postexposure, with a total detection rate of 53.33%, ranging from the limit of detection to 23.94 μg/L. In conclusion, protein-bound α-amanitin had a higher positive detection rate and a longer detection window than free α-amanitin in mice.

Investigation of In Vitro and In Vivo Metabolism of α-Amanitin in Rats Using Liquid Chromatography-Quadrupole Time-of-Flight Mass Spectrometric Method

The purpose of this study is to investigate the difference of in vitro-in vivo correlation of α-amanitin from clearance perspectives as well as to explore the possibility of extra-hepatic metabolism of α-amanitin. First, a liquid chromatography-quadrupole-time-of-flight-mass spectrometric (LC-qTOF-MS) method for α-amanitin in rat plasma was developed and applied to evaluate the in vitro liver microsomal metabolic stability using rat and human liver microsomes and the pharmacokinetics of α-amanitin in rat. The predicted hepatic clearance of α-amanitin in rat liver microsomes was quite low (5.05 mL/min/kg), whereas its in vivo clearance in rat (14.0 mL/min/kg) was close to the borderline between low and moderate clearance. To find out the difference between in vitro and in vivo metabolism, in vitro and in vivo metabolite identification was also conducted. No significant metabolites were identified from the in vivo rat plasma and the major circulating entity in rat plasma was α-amanitin itself. No reactive metabolites such as GSH-adducts were detected either. A glucuronide metabolite was newly identified from the in vitro liver microsomes samples with a trace level. A semi-mass balance study was also conducted to understand the in vivo elimination pathway of α-amanitin and it showed that most α-amanitin was mainly eliminated in urine as intact which implies some unknown transporters in kidney might play a role in the elimination of α-amanitin in rat in vivo. Further studies with transporters in the kidney would be warranted to figure out the in vivo clearance mechanism of α-amanitin.

Toxicokinetics of β-Amanitin in Mice and In Vitro Drug-Drug Interaction Potential

The toxicokinetics of β-amanitin, a toxic bicyclic octapeptide present abundantly in Amanitaceae mushrooms, was evaluated in mice after intravenous (iv) and oral administration. The area under plasma concentration curves (AUC) following iv injection increased in proportion to doses of 0.2, 0.4, and 0.8 mg/kg. β-amanitin disappeared rapidly from plasma with a half-life of 18.3−33.6 min, and 52.3% of the iv dose was recovered as a parent form. After oral administration, the AUC again increased in proportion with doses of 2, 5, and 10 mg/kg. Absolute bioavailability was 7.3−9.4%, which resulted in 72.4% of fecal recovery from orally administered β-amanitin. Tissue-to-plasma AUC ratios of orally administered β-amanitin were the highest in the intestine and stomach. It also readily distributed to kidney > spleen > lung > liver ≈ heart. Distribution to intestines, kidneys, and the liver is in agreement with previously reported target organs after acute amatoxin poisoning. In addition, β-amanitin weakly or negligibly inhibited major cytochrome P450 and 5′-diphospho-glucuronosyltransferase activities in human liver microsomes and suppressed drug transport functions in mammalian cells that overexpress transporters, suggesting the remote drug interaction potentials caused by β-amanitin exposure.