Toxic properties of the mushroom Cortinarius orellanus. I. Chemical characterization of the main toxin of Cortinarius orellanus (Fries) and Cortinarius speciosissimus (Kühn & Romagn) and acute toxicity in mice

Orellanine: From Fungal Origin to a Potential Future Cancer Treatment

Fungal metabolites represent an underutilized resource in the development of novel anticancer drugs. This review will focus on the promising fungal nephrotoxin orellanine, found in mushrooms including Cortinarius orellanus (Fools webcap). Emphasis will be placed on its historical significance, structural features, and associated toxicomechanics. Chromatographic methods for analysis of the compound and its metabolites, its synthesis, and chemotherapeutic potential are also discussed. Although orellanine's exceptional selectivity for proximal tubular cells is well documented, the mechanics of its toxicity in kidney tissue remains disputed. Here, the most commonly proposed hypotheses are detailed in the context of the molecule's structure, the symptoms seen following ingestion, and its characteristic prolonged latency period. Chromatographic analysis of orellanine and its related substances remains challenging, while biological evaluation of the compound is complicated by uncertainty regarding the role of active metabolites. This has limited efforts to structurally refine the molecule; despite numerous established methods for its synthesis, there is minimal published material on how orellanine's structure might be optimized for therapeutic use. Despite these obstacles, orellanine has generated promising data in preclinical studies of metastatic clear cell renal cell carcinoma, leading to the early 2022 announcement of phase I/II trials in humans.

Toxicity Assessment of Wild Mushrooms from the Western Ghats, India: An in Vitro and Sub-Acute in Vivo Study

Background: Poisoning by different kinds of toxic mushrooms is unfortunately becoming an increasingly important medical problem, evident from the growing number of reports worldwide since the 1950s. Mycetism being a health concern, deserves scientific attention. In this perspective, the present study aims to assess the potential effects of ingesting the selected wild mushrooms from regions of the Western Ghats, India.

Methods: The preliminary cytotoxicity of the selected mushrooms was studied in vitro on the intestinal NCM460 and the Chang's liver cell lines on the basis of cell viability. Further, the hepatotoxicity was assessed by measuring biologically relevant endpoints such as membrane integrity, mitochondrial stress and oxidative status. A 28 day sub-acute toxicity study was carried out by orally administering the mushroom extracts to mice at 250 and 500 mg/kg body weight. The hematological and serum analysis as well as histological examinations were carried out to evaluate their in vivo toxicity. GC-MS analysis of the mushrooms facilitated the identification of their volatile chemical profile.

Result: The in vitro intestinal cytotoxicity exhibited by these wild mushrooms in comparison to the edible mushroom indicated their potential gastrointestinal toxicity. The pathological findings in small intestine on exposure to Chlorophyllum molybdites and Agaricus endoxanthus also validates the speculations about their intestinal toxicity. The toxic insult to the hepatocytes due to Amanita angustilamellata, Entoloma crassum, and Clarkeinda trachodes was predictive of the observed in vivo hepatotoxicity which was also accompanied by renal toxicity at the higher dose of 500 mg/kg bwt.

Conclusion: The potential toxicity exhibited by these representative mushrooms from the wild warrants caution about their consumption. The present work could also have broader implications for global mycetism.

Long-term clinical outcome for patients poisoned by the fungal nephrotoxin orellanine

Background

Accidental intake of mushrooms of the Cortinarius species (deadly webcap) may cause irreversible renal damage and the need for dialysis or transplantation. The species is found in forests of Northern Europe, Scandinavia and North America and may be mistaken for other edible mushrooms. The highly selective nephrotoxic compound of the mushroom is called orellanine. Very little is known about the long-term effects of the nephrotoxin.

Methods

We identified patients who ingested deadly webcap in the period of 1979 to 2012. Informed consent and medical records were obtained for 28 of the 39 cases that occurred during the 34-year period. A case control group was also studied based on sex, age and initiation of dialysis or transplantation.

Results

The average age at time of the accidental intake was 40 ± 3 (n = 28) years. 64% of patients were male, and 22 of 28 patients developed acute kidney injury requiring dialysis. Serum creatinine peaked at 1 329 ± 133 μmol/l, and serum urea was 31 ± 3.5 mmol/l. No signs of acute damage were present in any other organ. The average time of follow-up was 16.9 ± 2.1 years (1.24–34.3 years, n = 28). 15 patients were transplanted and 3 also had a second graft. At follow-up, 23 patients were alive, and five had died at ages of 67 ± 5 (range 54–84). The outcome was similar in the case control group with 6 deaths in 20 patients.

Conclusion

We conclude that the long-term prognosis for patients poisoned by deadly webcap who lost their renal function is not different compared to other patients in active uremic care.

Human and experimental toxicology of orellanine

Orellanine is a nephrotoxic toxin produced by some mushroom species of the Cortinarius genus, typically found in Europe and North America. The nephrotoxicity of Cortinarius orellanus is well known and was first recognized in the 1950s when this mushroom was identified as the cause of a mass poisoning in Poland. Typically, onset of symptoms is delayed for 1-2 weeks after ingestion. Some patients suffer mild gastrointestinal discomfort in the latency period before developing signs of renal impairment due to severe interstitial nephritis, acute focal tubular damage, and interstitial fibrosis. There is no specific antidote to orellanine poisoning. The mainstay of treatment is the prevention of secondary complications of kidney failure, adequate dialysis and, in the case of incomplete recovery, management of chronic renal insufficiency. : In this work, we aim to review about Cortinarius species, including epidemiological studies, chemical structure, toxicokinetics, toxic doses, mechanisms of toxicity, diagnosis, prognosis, and treatment options.

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.

A novel orellanine containing mushroom Cortinarius armillatus

Orellanine (3,3',4,4'-tetrahydroxy-2,2'-bipyridine-1,1'-dioxide) is a tetrahydroxylated di-N-oxidized bipyridine compound. The toxin, present in certain species of Cortinarius mushrooms, is structurally similar to herbicides Paraquat and Diquat. Cortinarius orellanus and Cortinarius rubellus are the major orellanine-containing mushrooms. Cortinarius mushrooms are widely reported in Europe where they have caused human poisoning and deaths through accidental ingestion of the poisonous species mistaken for the edible ones. In North America, Cortinarius orellanosus mushroom poisoning was recently reported to cause renal failure in a Michigan patient. Cortinarius mushroom poisoning is characterized by delayed acute renal failure, with some cases progressing to end-stage kidney disease. There is debate whether other Cortinarius mushroom contain orellanine or not, especially in North America. Currently, there are no veterinary diagnostic laboratories in North America with established test methods for detection and quantitation of orellanine. We have developed two diagnostic test methods based on HPLC and LC-MSMS for identification and quantitation of orellanine in mushrooms. Using these methods, we have identified Cortinarius armillatus as a novel orellanine-containing mushroom in North America. The mean toxin concentration of 145 ug/g was <1% of that of the more toxic C. rubellus. The HPLC method can detect orellanine at 17 μg g(-1) while the LC-MSMS method is almost 2000 times more sensitive and can detect orellanine at 30 ng g(-1). Both tests are quantitative, selective and are now available for veterinary diagnostic applications.

Analysis of the mushroom nephrotoxin orellanine and its glucosides

Orellanine is a nephrotoxin found in various Cortinaceae mushroom species. Unintentional consumption after these species were confused with edible mushrooms such as Cantharellus tubaeformis has caused several casualties. In this work, a quantitative HPLC-ESI-MS/MS method for total orellanine in Cortinarius rubellus, spiked blood plasma, and a mushroom stew prepared from C. tubaeformis with the addition of a single specimen of C. rubellus is presented. The existence of mono- and diglucosylated orellanine in C. rubellus was also proven, although quantitative analysis could not be obtained for the glucosides due to rapid hydrolyzation to orellanine in the extract. Extraction with 3 M HCl or water mainly yielded orellanine, while MeOH or acidified MeOH mainly extracted mono- and diglucosylated orellanine. The highest recovery of total orellanine was obtained with 3 M HCl, which was subsequently used for quantitative analysis. A C₁₈ HPLC column and low pH in the eluents retained all these toxins. Orellanine could be detected at a 4.9 ng/mL level in all extracts, which is well below the threshold for acute toxic effects. Additionally, the fragmentation pattern of orellanine upon electrospray MS/MS was probed. The method described is useful for two important applications. First, it allows quantitative analysis of processed food products that may be contaminated by orellanine from Cortinaceae mushrooms. Second, orellanine is currently being evaluated as a potential cure of metastatic renal cancer, and this work provides a method for monitoring orellanine at low concentrations within the therapeutic interval in blood serum.

Mycotoxins revisited: Part I

Mushrooms are ubiquitous in nature. They are an important source of nutrition; however, certain varieties contain chemicals that can be highly toxic to humans. Industrially cultivated mushrooms are historically very safe, but foraging for mushrooms or accidental ingestion of mushrooms in the environment can result in serious illness and death. The emergency department is the most common site of presentation for patients suffering from acute mushroom poisoning. Although recognition can be facilitated by identification of a characteristic toxidrome, the presenting manifestations can be variable and have considerable overlap with more common and generally benign clinical syndromes. The goal of this two-part article is to review the knowledge base on this subject and provide information that will assist the clinician in the early consideration, diagnosis and treatment of mushroom poisoning. Part I, presented in this issue of the Journal, reviews the epidemiology and demographics of mushroom poisoning, the physical characteristics of the most toxic varieties, the classification of the toxic species, and an overview of the cyclopeptide-containing mushroom class. Part II, to be published in the next issue of the Journal, will be focused on the presentation of the other classes of toxic mushrooms along with an up-to-date review of the most recently identified poisonous varieties.

Treatment of intoxication with Cortinarius speciosissimus using an antioxidant therapy

The authors present the case reports of a 30-year-old man and his 29-year-old wife who ingested a mushroom meal containing Cortinarius speciosissimus. Features of this intoxication include gastrointestinal symptoms such as nausea, vomiting, and diarrhea as well as back pain. The toxin orellanine is nephrotoxic and can lead to acute renal failure. A long symptom-free interval of 2 to 21 days is characteristic of this poisoning. The diagnosis can be made by mycologic testing or by toxicologic analysis of a renal biopsy specimen. Reported therapeutic options include hemodialysis, plasmapheresis, or drug therapy with corticosteroids, all of which have yielded variable results. Here the authors report the use of antioxidant therapy in 2 patients with acute renal failure caused by Cortinarius speciosissimus intoxication.

Cytotoxic fungi—an overview

Among fungal toxins causing organ damage in the human body, amatoxins and orellanine remain exceptional. Amatoxins, a group of bicyclic octapeptides occurring in some Amanita, Galerina and Lepiota species, induce deficient protein synthesis resulting in cell death, but might also exert toxicity through inducing apoptosis. Target organs are intestinal mucosa, liver and kidneys. Poisoning will result in dehydration and electrolyte derangement, liver necrosis and possibly kidney damage. In established poisoning the mainstay of treatment is optimum symptomatic and supportive care. No specific treatment is available, but some pharmaceuticals, like silibinin, benzylpenicillin and acetylcysteine, might have a role in limiting the extent of hepatic damage. Orellanine is a nephrotoxic bipyridine N-oxide found in some Cortinarius species. Its mechanism of action is not fully understood, but it has been shown to inhibit protein synthesis and to generate free oxygen radicals. As early symptoms often are lacking or vague, poisoning may initially be overlooked or misinterpreted and the patients usually present with established renal damage. Supportive care is the only therapeutic option. Tricholoma equestre might contain a myotoxin and repeated ingestion may cause significant rhabdomyolysis. Ingestion of Amanita smithiana and A. proxima has been reported to result in kidney damage. Gyromitrin, a toxic compound that is converted to hydrazines in the stomach, occurs in some Gyromitra species. It is mainly neurotoxic, but may also induce moderate hepatic damage and haemolysis.

Main features of Cortinarius spp. poisoning: a literature review

INTRODUCTION

Cortinarius spp. poisoning is characterized by a delayed acute renal failure. The main features of this severe poisoning are still poorly known and often overlooked. The aim of this literature review is a better description of Cortinarius spp. poisoning.

MATERIALS AND METHODS

The main medical databases were searched: Abstracts of Mycology, Current Contents, Medline, Pascal, Micromedex Poisindex, Toxicology abstracts, Toxline. All case reports that included a description of the clinical features of Cortinarius spp. poisoning were studied.

RESULTS

245 cases were collected and 90 cases could be analyzed in details. Gastrointestinal disorders are the main symptoms of the prerenal phase of the poisoning. They appear a few days after the ingestion of the mushrooms (median 3 days). The renal phase is delayed (median 8.5 days). Moderate and transient hepatic abnormalities have been reported. A severe hepatic failure can be ruled out. Muscular lesions are highly questionable. Treatment is supportive. No specific treatment can be recommended. Acute renal failure progressed towards chronic renal failure in half of the cases; intermittent hemodialysis or kidney transplantations were necessary in 70% of those cases.

CONCLUSION

Cortinarius spp. poisoning is severe. Ingestion of Cortinarius species must be systematically suspected whenever tubulo-interstitial nephritis is diagnosed, especially as mushrooms may have been ingested 1-2 weeks before.

Novel methods for identification and quantification of the mushroom nephrotoxin orellanine. Thin-layer chromatography and electrophoresis screening of mushrooms with electron spin resonance determination of the toxin

Orellanine, (2,2'-bipyridine)-3,3',4,4'-tetrol-1,1'-dioxide, the toxin from several Cortinariace species, induces an acute renal failure which can be very severe or even irreversible and fatal. It is therefore important to be able to quickly and simply identify orellanine in mushroom samples with classical methods, readily available in any laboratory, such as anti-poison centers. This article reports the results of three analytical methods: classical TLC on cellulose plates in n-butanol--acetic acid--water and two original methods, electrophoresis on agarose gel and direct electron spin resonance (ESR) after enzymatic oxidation. They were applied to detect orellanine in 34 Cortinariaceae and 4 other species of toadstools. Our three sets of results are convergent. TLC (detection limit: 15 ng with fluorescence densitometry), electrophoresis (25 ng) and even ESR (5 micrograms), are sensitive enough for our purpose, and a sophisticated method like HPLC (detection limit: 50 pg) is not required. As the ESR spectrum of the toxin semiquinone is highly specific, TLC or electrophoresis coupled with ESR are a convenient alternative to liquid chromatography coupled with mass spectrometry, with the same specificity, for a confirmation or with samples such as ours with high toxin contents. ESR unambiguously confirms the relatively high contents of orellanine, from 0.45% (C. henrici) to 1.1-1.4% (C. orellanus), found in five Cortinarius from the subgenus Leprocybe, section Orellani. The five species, though they are from different geographic origins, have a more or less common pattern of fluorescent compounds, among which orellinine and orelline beside orellanine. It can be useful to note that orellanine semiquinone can be easily detected by ESR directly in the fresh mushroom. The toxin is absent in the other mushrooms we tested, especially in D. cinnamomea and C. splendens, which have been claimed as toxic and suspected to contain orellanine.

Toxic properties of the mushroom Cortinarius orellanus (Fries). II. Impairment of renal function in rats

Oral administration of the toxic mushroom Cortinarius orellanus (Fr.) to male Sprague Dawley rats caused serious impairment of renal function. The signs observed were similar to those produced in humans who ingest this fungus. Administration of 2.0 g dried Cortinarius orellanus per kg body weight led to acute renal dysfunction within 48 h. The pattern of impairment included reduced glomerular filtration rate, decreased renal absorption of water, sodium and potassium, and proteinuria and glucosuria. The nephrotoxic effect was further characterized by decreased activities of the brush border enzymes alkaline phosphatase and gamma-glutamyltranspeptidase in urine, despite a remarkable increase in protein excretion of predominantly tubular origin. These findings were substantiated by morphologic changes, which could be detected as early as 12 h after dosing. Morphologically discernible signs of renal tubular damage start with deformation of the proximal tubular brush border region. Within 48 h after toxin ingestion, prenecrotic and necrotic cells could be found in all nephron segments contained in the renal cortex. The most prominent changes were a vesiculation of the apical cell pole and a swelling of the smooth surfaced endoplasmic reticulum and of mitochondria. The latter was accompanied by a loss in matrix material and a massive fragmentation of mitochondrial cristae membranes. Detectable quantities of the toxic principle of the mushroom, orellanine, were excreted only within the first 24 h after dosing. No impairment of liver function was detected.