Mechanism and treatment of α-amanitin poisoning.

Amanita poisoning has a high mortality rate. The α-amanitin toxin in Amanita is the main lethal toxin. There is no specific detoxification drug for α-amanitin, and the clinical treatment mainly focuses on symptomatic and supportive therapy. The pathogenesis of α-amanitin mainly includes: α-amanitin can inhibit the activity of RNA polymeraseII in the nucleus, including the inhibition of the largest subunit of RNA polymeraseII, RNApb1, bridge helix, and trigger loop. In addition, α-amanitin acts in vivo through the enterohepatic circulation and transport system. α-Amanitin can cause the cell death. The existing mechanisms of cell damage mainly focus on apoptosis, oxidative stress, and autophagy. In addition to the pathogenic mechanism, α-amanitin also has a role in cancer treatment, which is the focus of current research. The mechanism of action of α-amanitin on the body is still being explored.

Liver transcriptome analyses of acute poisoning and recovery of male ICR mice exposed to the mushroom toxin α-amanitin.

Approximately 70-90% of mushroom poisoning deaths are caused by α-amanitin-induced liver injury resulting from RNA polymerase II (RNAP II) inhibition. Liver regeneration ability may contribute greatly to individual survival after α-amanitin poisoning. However, it is unclear what cellular pathways are activated to stimulate regeneration. We conducted dose-effect and time-effect studies in mice that were intraperitoneally injected with 0.33-0.66 mg/kg α-amanitin to establish a poisoning model. The liver/body weight ratio, serological indices, and pathology were evaluated to characterize the liver injury. In the time-effect study, the liver transcriptome was analyzed to explore the mRNA changes resulting from RNAP II inhibition and the underlying pathways associated with recovery. Based on the two animal studies, we established a poisoning model with three sequential liver states: early injury, regulation, and recovery. The mRNA changes reflected by the differentially expressed genes (DEGs) in the transcriptome could be used to illustrate the inhibition of RNAP II by α-amanitin. DEGs at four key time points were well matched with the three liver states, including 8-h downregulated genes in the early injury state, 16-h and 72-h upregulated genes in the regulation state, and 96-h upregulated/downregulated genes in the recovery state. By clustering analysis, the mTOR signaling pathway was screened out as the most promising potential pathway promoting recovery. The results of our investigations of the pathways and events downstream of the mTOR pathway indicated that the activation of mTOR probably contributes crucially to liver regeneration, which could be a promising basis for drug development.

Identification of Decrease in TRiC Proteins as Novel Targets of Alpha-Amanitin-Derived Hepatotoxicity by Comparative Proteomic Analysis In Vitro.

Alpha-amanitin (α-AMA) is a cyclic peptide and one of the most lethal mushroom amatoxins found in Amanita phalloides. α-AMA is known to cause hepatotoxicity through RNA polymerase II inhibition, which acts in RNA and DNA translocation. To investigate the toxic signature of α-AMA beyond known mechanisms, we used quantitative nanoflow liquid chromatography-tandem mass spectrometry analysis coupled with tandem mass tag labeling to examine proteome dynamics in Huh-7 human hepatoma cells treated with toxic concentrations of α-AMA. Among the 1828 proteins identified, we quantified 1563 proteins, which revealed that four subunits in the T-complex protein 1-ring complex protein decreased depending on the α-AMA concentration. We conducted bioinformatics analyses of the quantified proteins to characterize the toxic signature of α-AMA in hepatoma cells. This is the first report of global changes in proteome abundance with variations in α-AMA concentration, and our findings suggest a novel molecular regulation mechanism for hepatotoxicity.

Energy disorders caused by mitochondrial dysfunction contribute to α-amatoxin-induced liver function damage and liver failure.

Mushroom toxicity is the main branch of foodborne poisoning, and liver damage caused by amatoxin poisoning accounts for more than 90 % of deaths due to mushroom poisoning. Alpha-amatoxin (α-AMA) has been considered the primary toxin from amatoxin-containing mushrooms, which is responsible for hepatotoxicity and death. However, the mechanism underlying liver failure due to α-AMA remains unclear. This study constructed animal and cell models. In the animal experiments, we investigated liver injury in BALB/c mice at different time points after α-AMA treatment, and explored the process of inflammatory infiltration using immunohistochemistry and western blotting. Then, a metabonomics method based on gas chromatography mass spectrometry (GCMS) was established to study the effect of α-AMA on liver metabonomics. The results showed a significant difference in liver metabolism between the exposed and control mice groups that coincided with pathological and biochemical indicators. Moreover, 20 metabolites and 4 metabolic pathways related to its mechanism of action were identified, which suggested that energy disorders related to mitochondrial dysfunction may be one of the causes of death. The significant changes of trehalose and the fluctuation of LC3-II and sqstm1 p62 protein levels indicated that autophagy was also involved in the damage process, suggesting that autophagy may participate in the clearance process of damaged mitochondria after poisoning. Then, we constructed an α-AMA-induced human normal liver cells (L-02 cells) injury model. The above hypothesis was further verified by detecting cell necrosis, mitochondrial reactive oxygen species (mtROS), mitochondrial permeability transition pore (mPTP) opening, mitochondrial membrane potential (Δψ m), and cellular ATP level. Collectively, our results serve as direct evidence of elevated in vivo hepatic mitochondrial metabolism in α-AMA-exposed mice and suggest that mitochondrial dysfunction plays an important role in the early stage of α-AMA induced liver failure.

Toxic Potential of Traditionally Consumed Mushroom Species-A Controversial Continuum with Many Unanswered Questions.

Mushroom poisonings remain a significant cause of emergency medicine. While there are well-known species, such as Amanita phalloides, causing life-threatening poisonings, there is also accumulating evidence of poisonings related to species that have been considered edible and are traditionally consumed. In particular, the Tricholoma equestre group was reported to cause myotoxicity. In addition, particular wild mushrooms that are traditionally consumed especially in Asia and Eastern Europe have been subject to suspicion due to possible mutagenicity. Hitherto, the causative agents of these effects often remain to be determined, and toxicity studies have yielded contradictory results. Due to this, there is no consensus about the safety of these species. The issue is further complicated by difficulties in species identification and other possible sources of toxicity, such as microbiological contamination during storage, leading to sometimes opposite conclusions about the edibility of a species. This review focuses on existing data about these types of mushroom poisonings, including the still sparse knowledge about the causative chemical agents. In addition, the aim is to initiate a meta-discussion about the issue and to give some suggestions about how to approach the situation from the viewpoint of the collector, the researcher, and the practicing physician.

Mushroom poisoning from Inocybe serotina: A case report from Ningxia, northwest China with exact species identification and muscarine detection.

Mushroom poisoning is a serious food safety issue in China. However, there is insufficient information on many poisoning incidents, including mushroom species and their clinical manifestations, diagnosis, treatments and toxins. Detailed epidemiological investigation was conducted after the occurrence of a mushroom poisoning incident resulting in typical muscarinic syndrome in Ningxia, China. The suspected mushroom species was identified based on morphological and phylogenetic analyses. Muscarine was detected using ultrahigh-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). On September 2, 2019, two patients exhibited typical muscarinic syndrome after consuming wild mushrooms. The clinical manifestations included chills, sweating, salivation and diarrhoea; the incubation period was approximately 2 h. Treatments, including anti-inflammatory, detoxification and nutritional support, were remedial. Full recovery ensued within 24 h. The specimen was identified as Inocybe serotina, and its muscarine content was 324.0 ± 62.4 mg/kg (k = 2, p = 95%). Two patients were poisoned via stimulation of their parasympathetic nervous system due to mistaken consumption of muscarine-containing I. serotina. They fully recovered with supportive treatments. To our knowledge, this is the first case report of I. serotina poisoning worldwide and is the first record of this species in China. Further, a method for muscarine detection was established using UPLC-MS/MS.

In vitro mechanistic studies on α-amanitin and its putative antidotes.

α-Amanitin plays a key role in Amanita phalloides intoxications. The liver is a major target of α-amanitin toxicity, and while RNA polymerase II (RNA Pol II) transcription inhibition is a well-acknowledged mechanism of α-amanitin toxicity, other possible toxicological pathways remain to be elucidated. This study aimed to assess the mechanisms of α-amanitin hepatotoxicity in HepG2 cells. The putative protective effects of postulated antidotes were also tested in this cell model and in permeabilized HeLa cells. α-Amanitin (0.1-20 µM) displayed time- and concentration-dependent cytotoxicity, when evaluated through the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) reduction and neutral red uptake assays. Additionally, α-amanitin decreased nascent RNA synthesis in a concentration- and time-dependent manner. While α-amanitin did not induce changes in mitochondrial membrane potential, it caused a significant increase in intracellular ATP levels, which was not prevented by incubation with oligomycin, an ATP synthetase inhibitor. Concerning the cell redox status, α-amanitin did not increase reactive species production, but caused a significant increase in total and reduced glutathione, which was abolished by pre-incubation with the inhibitor of gamma-glutamylcysteine synthase, buthionine sulfoximine. None of the tested antidotes [N-acetyl cysteine, silibinin, benzylpenicillin, and polymyxin B (PolB)] conferred any protection against α-amanitin-induced cytotoxicity in HepG2 cells or reversed the inhibition of nascent RNA caused by the toxin in permeabilized HeLa cells. Still, PolB interfered with RNA Pol II activity at high concentrations, though not impacting on α-amanitin observed cytotoxicity. New hepatotoxic mechanisms of α-amanitin were described herein, but the lack of protection observed in clinically used antidotes may reflect the lack of knowledge on their true protection mechanisms and may explain their relatively low clinical efficacy.

A case study of Lepiota brunneoincarnata poisoning with endoscopic nasobiliary drainage in Shandong, China.

The most frequently reported fatal Lepiota ingestions are due to L. brunneoincarnata. We present a case of L. brunneoincarnata poisoning with endoscopic nasobiliary drainage known to be the first in China. The patient suffered gastrointestinal symptoms 9 h post ingestion of mushrooms. The patient was hospitalized 4 days after eating the mushrooms with jaundice. The peak ALT, AST, APTT, TBIL and DBIL values of the patient were as follow: ALT, 2980 U/L (day 4 post ingestion); AST, 1910 U/L (day 4 post ingestion); APTT, 92.8 seconds (day 8 post ingestion), TBIL, 136 µmol/L (day 10 post ingestion), DBIL 74 µmol/L (day 10 post ingestion). UPLC-ESI-MS/MS was used to detect the peptide toxins in the mushroom and biological samples from the patient. We calculated that the patient may have ingested a total of 29.05 mg amatoxin from 300 g mushrooms, consisting of 19.91 mg α-amanitin, 9.1 mg ß-amanitin, and 0.044 mg γ-amanitin. Amatoxins could be detected in bile even on day 6 after ingestion of L. brunneoincarnata. With rehydration, endoscopic nasobiliary drainage and intravenous infusion of Legalon SIL, the patient recovered after serious hepatotoxicity developed.

Improved Tissue-Based Analytical Test Methods for Orellanine, a Biomarker of Cortinarius Mushroom Intoxication.

Orellanine (OR) toxin is produced by mushrooms of the genus Cortinarius which grow in North America and in Europe. OR poisoning is characterized by severe oliguric acute renal failure, with a mortality rate of 10%-30%. Diagnosis of OR poisoning currently hinges on a history of ingestion of Cortinarius mushrooms and histopathology of renal biopsies. A key step in the diagnostic approach is analysis of tissues for OR. Currently, tissue-based analytical methods for OR are nonspecific and lack sensitivity. The objectives of this study were: (1) to develop definitive HPLC and LC-MS/MS tissue-based analytical methods for OR; and (2) to investigate toxicological effects of OR in mice. The HPLC limit of quantitation was 10 µg/g. For fortification levels of 15 µg/g to 50 µg/g OR in kidney, the relative standard deviation was between 1.3% and 9.8%, and accuracy was within 1.5% to 7.1%. A matrix-matched calibration curve was reproduced in this range with a correlation coefficient (r) of 0.97-0.99. The limit of detection was 20 ng/g for LC-MS/MS. In OR-injected mice, kidney OR concentrations were 97 ± 51 µg/g on Day 0 and 17 ± 1 µg/g on termination Day 3. Splenic and liver injuries were novel findings in this mouse model. The new tissue-based analytical tests will improve diagnosis of OR poisoning, while the mouse model has yielded new data advancing knowledge on OR-induced pathology. The new tissue-based analytical tests will improve diagnosis of OR poisoning, while the mouse model has yielded new data advancing knowledge on OR-induced pathology.

Production of (15)N-labeled α-amanitin in Galerina marginata.

α-Amanitin is the major causal constituent of deadly Amanita mushrooms that account for the majority of fatal mushroom poisonings worldwide. It is also an important biochemical tool for the study of its target, RNA polymerase II. The commercial supply of this bicyclic peptide comes from Amanita phalloides, the death cap mushroom, which is collected from the wild. Isotopically labeled amanitin could be useful for clinical and forensic applications, but α-amanitin has not been chemically synthesized and A. phalloides cannot be cultured on artificial medium. Using Galerina marginata, an unrelated saprotrophic mushroom that grows and produces α-amanitin in culture, we describe a method for producing (15)N-labeled α-amanitin using growth media containing (15)N as sole nitrogen source. A key to success was preparing (15)N-enriched yeast extract via a novel method designated "glass bead-assisted maturation." In the presence of the labeled yeast extract and (15)N-NH4Cl, α-amanitin was produced with >97% isotope enrichment. The labeled product was confirmed by HPLC, high-resolution mass spectrometry, and NMR.

Case series: Alcohol intolerance with Coprine-like syndrome after consumption of the mushroom Lepiota aspera (Pers.:Fr.) Quél., 1886 (Freckled Dapperling).

Alcohol intolerance after consumption of wild mushrooms is a recognized phenomenon. This is best understood with Coprinus atramentarius. Its active component Coprine blocks enzymatic ethanol degradation at the stage of acetaldehyde, which is responsible for the well-recognized symptoms. Here, we report three events in five patients experiencing the same symptoms after consumption of self-collected Lepiota aspera. All had mistaken L. aspera for edible mushrooms as Amanita rubescens or Macrolepiota procera. In all events, L. aspera was identified by mycologists and no other mushrooms were involved. The mushrooms were well sautéed and tolerated well until an alcoholic beverage was consumed. Then within few minutes facial flushing, throbbing headache, tachycardia, and shortness of breath all occurred. The symptoms abated within a few hours with no sequelae but could be re-provoked by further alcohol consumption up to 48 h later. This syndrome appears to be identical with the one known from C. atramentarius. However, the toxin in L. aspera or its mechanism is not yet known.

[Determination of illudin S in Omphalotus guepiniformis and foods that caused food poisoning by liquid chromatography with tandem mass spectrometry].

A simple method was developed for determination of illudin S in fungi (Omphalotus guepiniformis: poisonous mushroom) and a food that caused food poisoning, using liquid chromatography tandem mass spectrometry (LC/MS/MS). Illudin S in fungi and the food that caused food poisoning was extracted with methanol and then cleaned up with an Oasis HLB cartridge. LC separation was performed with an octadecylated silica column (Inertsil ODS-3, 2.1 mm i.d. x 150 mm) and a mobile phase of 0.1% formic acid-methanol (7 : 3) at a flow rate 0.2 mL/min. Mass spectral acquisition was performed in the positive mode and illudin S was targeted using multiple reaction monitoring (MRM) with electrospray ionization (ESI). The recoveries of illudin S were 84-94% from edible fungi (Lentinula edodes, Pleurotus ostreatus and Panellus serotinus). The detection limits of illudin S in the fungi (L. edodes, P. ostreatus and P. serotinus) were 0.08-0.10 microg/g respectively. Illudin S was detected in the food that caused food poisoning at the level of 2.0 and 15.1 microg/g in the soup and fungi, respectively. The recovery of illudin S from a mushroom soup (cooked at 100 degrees C for 10 min) sample which simulated food poisoning was 74.8%. These results indicate that the developed method is suitable for the determination of illudin S in fungi (O. guepiniformis) and foods that caused food poisoning.

In vitro inhibition of OATP-mediated uptake of phalloidin using bile acid derivatives.

Hepatocyte uptake of phalloidin is carried out mainly by OATP1B1. We have used this compound as a prototypic substrate and assayed the ability to inhibit OATP-mediated phalloidin transport of four bile acid derivatives (BALU-1, BALU-2, BALU-3 and BALU-4) that showed positive results in preliminary screening. Using Xenopus laevis oocytes for heterologous expression of transporters, BALUs were found to inhibit taurocholic acid (TCA) transport by OATP1B1 (but not OATP1B3) as well as by rat Oatp1a1, Oatp1a4 and Oatp1b2. The study of their ability to inhibit sodium-dependent bile acid transporters revealed that the four BALUs induced an inhibition of rat Asbt-mediated TCA transport, which was similar to TCA-induced self-inhibition. Regarding human NTCP and rat Ntcp, BALU-1 differs from the other three BALUS in its lack of effect on TCA transport by these proteins. Using HPLC-MS/MS and CHO cells stably expressing OATP1B1 the ability of BALU-1 to inhibit the uptake of phalloidin itself by this transporter was confirmed. Kinetic analysis using X. laevis oocytes revealed that BALU-1-induced inhibition of OATP1B1 was mainly due to a competitive mechanism (Ki=8 microM). In conclusion, BALU-1 may be useful as a pharmacological tool to inhibit the uptake of compounds mainly taken up by OATP1B1 presumably without impairing bile acid uptake by the major carrier accounting for this process, i.e., NTCP.

Excitatory actions of mushroom poison (acromelic acid) on unmyelinated muscular afferents in the rat.

Ingestion of a poisonous mushroom, Clitocybe acromelalga, results in strong and long-lasting allodynia, burning pain, redness and swelling in the periphery of the body. Acromelic acid (ACRO), a kainate analogue isolated from the mushroom, is assumed to be involved in the poisoning. ACRO has two isomers, ACRO-A and ACRO-B. The potency of ACRO-A is a million times higher than that of ACRO-B for induction of allodynia when intrathecally administered in mice. The effect of ACRO on the primary afferents of somatic tissues remains largely unknown. The aim of the present study was to examine the effect of ACRO-A on the response behavior of unmyelinated afferents in the skeletal muscle. For this purpose single fiber recordings of C-afferents were made from rat extensor digitorum longus (EDL) muscle-common peroneal nerve preparations in vitro. Intramuscular injections of ACRO-A at three different concentrations (10(-12), 10(-10) and 10(-8)M, 5 microl over 5s) near the receptive field in the EDL muscle elicited excitation of C-afferents (12%, 50% and 44%, respectively). ACRO-A at the concentration of 10(-10)M induced the strongest excitation. The incidence of ACRO-A responsive fibers at the concentration of 10(-10) and 10(-8)M was significantly higher than that at 10(-12)M. The responses to mechanical and heat stimulations did not differ between ACRO-A sensitive and insensitive fibers. These results clearly demonstrated the powerful excitatory action of ACRO-A on mechanosensitive unmyelinated afferents in the rat skeletal muscle.

The fungal nephrotoxin orellanine simultaneously increases oxidative stress and down-regulates cellular defenses.

Confusion of various nephrotoxic Cortinarius species with edible mushrooms occurs every year throughout Europe and North America. The toxin, orellanine (OR), accumulates selectively in renal tubular epithelium with ensuing renal failure after several days as the only clinical manifestation. This study was performed to clarify the mechanisms behind the kidney damage. Sprague-Dawley rats, 100 g bw, received various doses of purified OR ip (0-5 mg/kg bw). One week later, renal function (GFR) was determined (51Cr-EDTA), ascorbyl radicals in venous blood were analyzed using electron spin resonance, and oxidative protein damage was evaluated immunohistochemically. One OR-treated group (3.5 mg/kg) simultaneously received superoxide dismutase (SOD) targeted to tubular epithelium (HC-SOD; 10 mg/kg ip daily for 5 days). RT-PCR was used for analysis of mRNA expression of genes related to oxidative stress. OR caused a dose-dependent decrease in GFR, paralleled by increased levels of ascorbyl radicals and oxidative protein damage. Antioxidant treatment with HC-SOD decreased renal function even more and also increased tissue damage and mortality. Renal mRNA levels for key components in the antioxidative defense were strongly decreased, whereas those for several cytokines were increased. The data strongly suggest that OR nephrotoxicity in vivo is mediated by oxidative stress, including a virtual shutdown of important antioxidative enzymes. We interpret the unexpected effect of HC-SOD in terms of unbalanced SOD and catalase levels in the presence of OR, leading to massive generation of *OH and cell death.

Indications of hepatic and cardiac toxicity caused by subchronic Tricholoma flavovirens consumption.

The yellow tricholoma (Tricholoma flavovirens or Tricholoma equestre) is a wild mushroom species that was previously considered edible and tasty. Recently, it caused several cases of delayed rhabdomyolysis in humans and elevated serum creatine kinase (CK) activities in laboratory mice (Mus musculus) in a dose-response study. The present study continued to examine the effects of prolonged T. flavovirens consumption at 12 g freshly frozen mushroom kg(-1)d(-1) on the plasma clinical chemistry and organ histology of mice. The plasma CK and CK-MB activities and the plasma bilirubin concentrations were higher in the exposed mice than in the controls. In addition, pericardial lymphocyte infiltrates were present in the mice that had consumed the mushroom. The results indicate myo-, cardio- and hepatotoxic effects of T. flavovirens.

Pathological effects of the mushroom toxin alpha-amanitin on BALB/c mice.

The pathological effects of alpha-amanitin on BALB/c mice after receiving intravenous injection were evaluated by RP-HPLC and mouse genome oligonucleotide microarray. The content of alpha-amanitin in Amanita virosa was about 2833.8 microg/g dry fruiting body. The liver and kidneys showed critical pathological changes after alpha-amanitin poisoning, and sera BUN, Crea, ALT, AST, TBIL and DBIL were the sensitive markers. The compound alpha-amanitin was detected in liver and kidney tissue homogenates by RP-HPLC after 48 h. The results of mouse genome oligonucleotide microarray showed 146 genes' expression changed, which formed the alternant network. The expression of 66 genes decreased, while 80 ones increased with more than two-fold differential expression after 48 h. The compound alpha-amanitin influenced not only RNA polymerase II, but also the expression of its associated genes. The application of mouse oligo chip provided valuable data for further understanding the biological properties and molecular pathogenesis of alpha-amanitin, also might be helpful for screening the curative drug for alpha-amanitin intoxication.

Effects of Amanita phalloides toxins on insulin release: in vivo and in vitro studies.

The clinical picture of Amanita phalloides poisoning includes hypoglycaemia, usually related to hepatic damage. In fact, Amanita toxins induce hepatic glycogen depletion in humans and animals. However, in animals morphological changes of pancreatic beta cells are reported, suggesting that an alteration of insulin secretion might be involved in the pathogenesis of hypoglycaemia. Therefore, we determined fasting glucose, insulin and C-peptide levels in ten patients intoxicated by Amanita phalloides and in ten control subjects. Fasting blood samples were drawn on 3 consecutive days, beginning 48-72 h after mushroom ingestion, and glucose, insulin and C-peptide concentrations were determined by routine methods. Serum glucose concentrations did not differ between poisoned subjects and controls, whereas insulin and C-peptide concentrations were significantly higher in poisoned subjects ( P<0.01), with a significant positive correlation ( R=0.97, P<0.001). We also evaluated the effects of alpha-amanitin, the main amatoxin, on in vitro insulin release. Rat islets were incubated with 5 and 50 mg/l alpha-amanitin, in the presence or absence of 5.6 mM glucose. In another protocol, islets were preincubated for 2 h with 5 and 50 mg/l alpha-amanitin in medium containing 5.6 mM glucose. After lavage, islets were incubated with increasing glucose (2.8-22.0 mM) to evaluate insulin release. In vitro, both concentrations of toxin induced insulin release (5 mg/l P<0.02, 50 mg/l P<0.01 vs controls), in the presence of 5.6 mM glucose. Islets preincubated with 5 mg/l alpha-amanitin showed a pattern of glucose-stimulated insulin release similar to controls, whereas islets preincubated with 50 mg/l alpha-amanitin showed an increased basal release with a reduced response to glucose stimulation. These observations show that Amanita toxins might play a role in the clinical context of Amanita poisoning. We demonstrate, for the first time, that alpha-amanitin induces insulin release and may exert a cytotoxic effect on beta cells.