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

Evaluation of peritoneal dialysis prescriptions in uremic rats

BACKGROUND

Patients with end-stage kidney disease (ESKD) require dialysis or transplantation for their survival. There are few experimental animal models mimicking the human situation in which the animals are dependent on dialysis for their survival. We developed a peritoneal dialysis (PD) system for rats to enable long-term treatment under controlled conditions.

METHOD

Rats were chemically nephrectomised using orellanine to render them uremic. Two studies were performed, the first with highly uremic rats on PD for 5 days, and the other with moderately uremic rats on PD for 21 days. Blood and dialysate samples were collected repeatedly from the first study and solute concentrations analysed. Based on these values, dialysis parameters were calculated together with generation rates allowing for kinetic modelling of the effects of PD. In the second study, the general conditions of the rats were evaluated during a longer dialysis period.

RESULTS

For rats with estimated glomerular filtration rate (GFR) 5-10% of normal (moderately uremic rats), five daily PD cycles kept the rats in good condition for 3 weeks. For highly uremic rats (GFR below 3% of normal), more extensive dialysis is needed to maintain homeostasis and our simulations show that a six daily and four nightly PD cycles should be needed to keep the rats in good condition.

CONCLUSION

In conclusion, the PD system described in this study can be used for long-term studies of PD on uremic dialysis-dependent rats mimicking the human setting. To maintain whole body homeostasis of highly uremic rats, intense PD is needed during both day and night.

Toxicity induced by orellanine from the mushroom Cortinarius orellanus in primary renal tubular proximal epithelial cells (RPTEC): Novel mechanisms of action

The toxicity of Orellanine (OR), a significant factor in mushroom poisoning, has severe effects on the kidneys, particularly the proximal tubules. This study investigated the acute toxicity of OR from the Cortinarius orellanus mushroom in human Primary Renal Tubular Proximal Epithelial Cells (RPTEC). Additionally, the half maximal inhibitory concentration (IC50) of OR in MCF-7 cells was established. RPTEC were subjected to a 6.25 μg/ml dose of orellanine for 24 h, while Control cells were exposed to 0.05% DMSO (vehicle). The RT2 Profiler™ PCR Array Human Nephrotoxicity was utilized to identify genes that were upregulated or downregulated. Western blotting confirmed the protein product of some significantly regulated genes compared to control cells. The IC50 of OR was found to be 319.2 μg/ml. The mechanism of OR toxicity involved several pathways including apoptosis, metal ion binding, cell proliferation, tissue remodeling, xenobiotic metabolism, transporters, extracellular matrix molecules, and cytoskeleton pathways. Other genes from non-specific pathways were also identified. These findings enhance our understanding of OR nephrotoxicity and pave the way for future research into potential treatments or antidotes for natural mushroom poisoning.

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.

Mushroom Toxins: Chemistry and Toxicology

Mushroom consumption is a global tradition that is still gaining popularity. However, foraging for wild mushrooms and accidental ingestion of toxic mushrooms can result in serious illness and even death. The early diagnosis and treatment of mushroom poisoning are quite difficult, as the symptoms are similar to those caused by common diseases. Chemically, mushroom poisoning is related to very powerful toxins, suggesting that the isolation and identification of toxins have great research value, especially in determining the lethal components of toxic mushrooms. In contrast, most of these toxins have remarkable physiological properties that could promote advances in chemistry, biochemistry, physiology, and pharmacology. Although more than 100 toxins have been elucidated, there are a number of lethal mushrooms that have not been fully investigated. This review provides information on the chemistry (including chemical structures, total synthesis, and biosynthesis) and the toxicology of these toxins, hoping to inspire further research in this area.

Enzyme-Activated Generation of Reactive Oxygen Species from Heterocyclic N-Oxides under Aerobic and Anaerobic Conditions and Its Relevance to Hypoxia-Selective Prodrugs

Enzymatic one-electron reduction of heterocyclic N-oxides can lead to the intracellular generation of reactive oxygen species via several different chemical pathways. These reactions may be relevant to hypoxia-selective anticancer drugs, antimicrobial agents, and unwanted toxicity of heterocylic nitrogen compounds.

Pharmacokinetic Properties of the Nephrotoxin Orellanine in Rats

Orellanine is a nephrotoxin found in mushrooms of the Cortinarius family. Accidental intake of this substance may cause renal failure. Orellanine is specific for proximal tubular cells and could, therefore, potentially be used as treatment for metastatic renal cancer, which originates from these cells. However, more information is needed about the distribution and elimination of orellanine from the body to understand its potential use for therapy. In this study, 5 mg/kg orellanine (unlabeled and ³H-labeled) was injected intravenously in rats (Wistar and Sprague Dawley). Distribution was measured (Wistar rats, n = 10, n = 12) using radioluminography and the highest amount of orellanine was found in the kidney cortex and bladder at all time-points investigated. The pharmacokinetic properties of orellanine were investigated using LC-MS/MS and β-scintillation to measure the amount of orellanine in plasma. Three groups of rats were investigated: control rats with intact kidneys (n = 10) and two groups with bilateral renal artery ligation (n = 7) where animals in one of these groups were treated with peritoneal dialysis (n = 8). Using LC-MS/MS, the half-life of orellanine was found to be 109 ± 6 min in the controls. In the groups with ligated renal arteries, orellanine had a half-life of 756 ± 98 min without and 238 ± 28 min with dialysis. Thus, orellanine was almost exclusively eliminated by glomerular filtration as well as by peritoneal dialysis.

Orellanine specifically targets renal clear cell carcinoma

Renal cell carcinoma (RCC), arising from the proximal tubule in the kidney, accounts for approximately 85% of kidney cancers and causes over 140,000 annual deaths worldwide. In the last decade, several new therapies have been identified for treatment of metastatic RCC. Although these therapies increase survival time compared to standard care, none of them has curative properties. The nephrotoxin orellanine specifically targets proximal tubular epithelial cells, leaving other organs unaffected. We therefore hypothesized that the selective toxicity of orellanine extends to clear cell RCC (ccRCC) cells since they emanate from proximal tubular cells. Orellanine would thus target both primary and metastatic ccRCC in vitro and in vivo. We found that orellanine induces dose-dependent cell death in proximal tubular cells and in all ccRCC cells tested, both primary and cell lines, with no toxicity detected in control cells. The toxic action of orellanine involve decreased protein synthesis, disrupted cell metabolism and induction of apoptosis. In nude rats carrying human ccRCC xenografts, brief orellanine treatment eliminated more than 90% of viable tumor mass compared to control rats. This identifies orellanine as a potential treatment concept for ccRCC patients on dialysis, due to its unique selective toxicity towards ccRCC.

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.

Renal involvement in mushroom poisoning: The case of Orellanus syndrome

Although mushroom poisoning is a rare cause of acute renal injury, in some cases it may lead to the development of a severe and irreversible renal failure. Orellanus syndrome is the most important example of organic renal damage related to mushroom consumption. It is caused by the ingestion of orellanine, the main toxin of different types of Cortinarius mushrooms (Cortinarius speciosissimus, C. orellanus, C. orellanoides, etc.), and it is characterized by progressive clinical phases with a predominant kidney involvement, finally requiring renal replacement therapy in about 10% of cases. Renal damage is often late and associated with a histological picture of interstitial nephritis. Diagnosis is essentially clinical and no specific therapy has been shown to be effective in preventing and treating renal damage. Here, we describe the case of a patient with mixed wild mushroom poisoning, presenting the typical clinical signs and course of the Orellanus syndrome. This case offers us the opportunity to review the main clinical features of this severe and little-known intoxication.

Alpha-Amanitin Poisoning, Nephrotoxicity and Oxidative Stress: An Experimental Mouse Model

BACKGROUND

Alpha-amanitin (α-AMA) plays a major role in Amanita phalloides poisoning, showing toxic effects on multi-organs, particularly on the liver and kidneys. Studies have shown a relationship between α-AMA-related injuries and reactive oxygen species.

OBJECTIVES

We aimed to investigate whether there is renal injury and its relationship with oxidative stress after intraperitoneal injection of α-AMA in mice experimental poisoning models.

MATERIALS AND METHODS

There were 37 male BALB/c laboratory mice treated with α-AMA, according to the study groups: control group (n = 7); low dose (0.2 mg/kg) (n = 10); moderate dose (0.6 mg/kg) (n = 10), and high dose (1 mg/kg) (n = 10). The sample size was detected according to the ethical committee's decision as well as similar studies in the literature. After a 48-hour follow-up period, all the subjects were sacrificed for pathological and biochemical assays. The study was held in Turkey.

RESULTS

α-AMA poisoning in mice results in inflammatory changes and necrosis in renal structures. There were statistically significant differences between the study groups regarding measured levels of catalase, superoxide dismutase, glutathione peroxidase, total antioxidant status (TAS), total oxidant status (TOS) and malonyl dialdehyde in renal homogenates of mice (P < 0.001, P < 0.001, P < 0.001, P < 0.001, P < 0.001, and P = 0.001, respectively). The TOS and TAS measurements helped to eliminate cumbersome analysis of diverse oxidant and antioxidant molecules. The TOS levels in renal homogenate of mice were significantly higher in all the intoxication groups compared to the control group (5.73, 7.02, 7.77, and 9.65 mmol trolox eq/g protein and P = 0.002, P = 0.001, and P = 0.001, respectively). The TAS levels in moderate and high-dose groups were significantly lower than all the other groups treated with α-AMA (0.130, 0.152, 0.065, and 0.087 mmol trolox eq/g protein and P = 0.031, P = 0.001, and P = 0.001, respectively).

CONCLUSIONS

Our results indicated that α-AMA poisoning in mice led to inflammatory changes and necrosis in renal structures. Biochemical analysis showed a shift in the oxidative/anti-oxidative balance towards the oxidative status.

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.

Review of current and "omics" methods for assessing the toxicity (genotoxicity, teratogenicity and nephrotoxicity) of herbal medicines and mushrooms

ETHNOPHARMACOLOGICAL RELEVANCE

The increasing use of traditional herbal medicines around the world requires more scientific evidence for their putative harmlessness. To this end, a plethora of methods exist, more or less satisfying. In this post-genome era, recent reviews are however scarce, not only on the use of new "omics" methods (transcriptomics, proteomics, metabonomics) for genotoxicity, teratogenicity, and nephrotoxicity assessment, but also on conventional ones.

METHODS

The present work aims (i) to review conventional methods used to assess genotoxicity, teratogenicity and nephrotoxicity of medicinal plants and mushrooms; (ii) to report recent progress in the use of "omics" technologies in this field; (iii) to underline advantages and limitations of promising methods; and lastly (iv) to suggest ways whereby the genotoxicity, teratogenicity, and nephrotoxicity assessment of traditional herbal medicines could be more predictive.

RESULTS

Literature and safety reports show that structural alerts, in silico and classical in vitro and in vivo predictive methods are often used. The current trend to develop "omics" technologies to assess genotoxicity, teratogenicity and nephrotoxicity is promising but most often relies on methods that are still not standardized and validated.

CONCLUSION

Hence, it is critical that toxicologists in industry, regulatory agencies and academic institutions develop a consensus, based on rigorous methods, about the reliability and interpretation of endpoints. It will also be important to regulate the integration of conventional methods for toxicity assessments with new "omics" technologies.