Specificity of the ergothioneine transporter natively expressed in HeLa cells

Ergothioneine and mitochondria: An important protective mechanism?

Mitochondrial dysfunction is implicated in a wide range of human disorders including many neurodegenerative and cardiovascular diseases, metabolic diseases, cancers, and respiratory disorders. Studies have suggested the potential of l-ergothioneine (ET), a unique dietary thione, to prevent mitochondrial damage and improve disease outcome. Despite this, no studies have definitively demonstrated uptake of ET into mitochondria. Moreover, the expression of the known ET transporter, OCTN1, on the mitochondria remains controversial. In this study, we utilise mass spectrometry to demonstrate direct ET uptake in isolated mitochondria as well as its presence in mitochondria isolated from ET-treated cells and animals. Mitochondria isolated from OCTN1 knockout mice tissues, have impaired but still detectable ET uptake, raising the possibility of alternative transporter(s) which may facilitate ET uptake into the mitochondria. Our data confirm that ET can enter mitochondria, providing a basis for further work on ET in the prevention of mitochondrial dysfunction in human disease.

Are age-related neurodegenerative diseases caused by a lack of the diet-derived compound ergothioneine?

We propose that the diet-derived compound ergothioneine (ET) is an important nutrient in the human body, especially for maintenance of normal brain function, and that low body ET levels predispose humans to significantly increased risks of neurodegenerative (cognitive impairment, dementia, Parkinson's disease) and possibly other age-related diseases (including frailty, cardiovascular disease, and eye disease). Hence, restoring ET levels in the body could assist in mitigating these risks, which are rapidly increasing due to ageing populations globally. Prevention of neurodegeneration is especially important, since by the time dementia is usually diagnosed damage to the brain is extensive and likely irreversible. ET and vitamin E from the diet may act in parallel or even synergistically to protect different parts of the brain; both may be "neuroprotective vitamins". The present article reviews the substantial scientific basis supporting these proposals about the role of ET.

Ergothioneine Prevents Neuronal Cell Death Caused by the Neurotoxin 6-Hydroxydopamine

Neuronal cell death is a key mechanism involved in the development and exacerbation of Parkinson's disease (PD). The excessive production of reactive oxygen species (ROS) is a major cause leading to neuronal death; therefore, compounds that prevent oxidative stress-dependent neuronal death may be promising as a preventive method for PD. Ergothioneine is a natural amino acid with antioxidant properties, and its protective functions in the body are attracting attention. However, there has been no investigation into the protective functions of ergothioneine using in vivo and in vitro PD models. Thus, in this study, we analyzed the efficacy of ergothioneine against 6-hydroxydopamine (6-OHDA)-dependent neuronal cell death using immortalized hypothalamic neurons (GT1-7 cells). First, we found that ergothioneine prevents 6-OHDA-dependent neuronal cell death by suppressing ROS overproduction in GT1-7 cells. The cytoprotective effect of ergothioneine was partially abolished by verapamil, an inhibitor of OCTN1, which is involved in ergothioneine uptake. Furthermore, ergothioneine-rich Rice-koji (Ergo-koji) showed cytoprotective and antioxidant effects similar to those of ergothioneine. Taken together, these results suggest that ergothioneine or foods containing ergothioneine may be an effective method for preventing the development and progression of PD.

Protection against Doxorubicin-Induced Cardiotoxicity by Ergothioneine

Background: Anthracyclines such as doxorubicin remain a primary treatment for hematological malignancies and breast cancers. However, cardiotoxicity induced by anthracyclines, possibly leading to heart failure, severely limits their application. The pathological mechanisms of anthracycline-induced cardiac injury are believed to involve iron-overload-mediated formation of reactive oxygen species (ROS), mitochondrial dysfunction, and inflammation. The dietary thione, ergothioneine (ET), is avidly absorbed and accumulated in tissues, including the heart. Amongst other cytoprotective properties, ET was shown to scavenge ROS, decrease proinflammatory mediators, and chelate metal cations, including Fe²⁺, preventing them from partaking in redox activities, and may protect against mitochondrial damage and dysfunction. Plasma ET levels are also strongly correlated to a decreased risk of cardiovascular events in humans, suggesting a cardioprotective role. This evidence highlights ET's potential to counteract anthracycline cardiotoxicity. Methods and Findings: We investigated whether ET supplementation can protect against cardiac dysfunction in mice models of doxorubicin-induced cardiotoxicity and revealed that it had significant protective effects. Moreover, ET administration in a mouse breast cancer model did not exacerbate the growth of the tumor or interfere with the chemotherapeutic efficacy of doxorubicin. Conclusion: These results suggest that ET could be a viable co-therapy to alleviate the cardiotoxic effects of anthracyclines in the treatment of cancers.

Protective Effect of Ergothioneine Against Stroke in Rodent Models

Ergothioneine (ET) is a naturally occurring antioxidant and cytoprotective agent that is synthesized by fungi and certain bacteria. Recent studies have shown a beneficial effect of ET on neurological functions, including cognition and animal models of depression. The aim of this study is to elucidate a possible effect of ET in rodent models of stroke. Post-ischemic intracerebroventricular (i.c.v.) infusion of ET significantly reduced brain infarct volume by as early as 1 day after infusion in rats, as shown by triphenyltetrazolium chloride (TTC) assay. There was a dose-dependent increase in protection, from 50 to 200 ng of ET infusion. These results suggest that ET could have a protective effect on CNS neurons. We next elucidated the effect of systemic ET on brain infarct volume in mice after stroke. Daily i.p. injection of 35 mg/kg ET (the first dose being administered 3 h after stroke) had no significant effect on infarct volume. However, daily i.p. injections of 70 mg/kg, 100 mg/kg, 125 mg/kg and 150 mg/kg ET, with the first dose administered 3 h after stroke, significantly decreased infarct volume at 7 days after vessel occlusion in mice. In order to elucidate at what time interval during the 7 days there could be effective protection, a second set of experiments was carried out in mice, using one of the effective loading protocols, i.e. 125 mg/kg i.p. ET but the brains were analyzed at 1, 4 and 7 days post-stroke by MRI. We found that ET was already protective against neuronal injury and decreased the size of the brain infarct from as early as 1 day post-stroke. Behavioral experiments carried out on a third set of mice (using 125 mg/kg i.p. ET) showed that this was accompanied by significant improvements in certain behaviors (pole test) at 1 day after stroke. Together, results of this study indicate that i.c.v. and systemic ET are effective in reducing brain infarct volume after stroke in rodent models.

Determination of L-Ergothioneine in Cosmetics Based on Ultraperformance Liquid Chromatography-Tandem Mass Spectrometry

A new method was developed for the identification and determination of L-ergothioneine in cosmetics based on ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The pretreatment method, chromatographic column, chromatographic conditions, and mass spectrometric conditions of cosmetic samples were optimized. Methanol was chosen as the extraction solvent, 85% acetonitrile with 0.1% FA was selected as the mobile phase, and the Waters CORTECS UPLC hydrophilic interaction liquid chromatography (HILIC) column was chosen for the separation. The sample was extracted with methanol and filtered, then separated by HILIC and detected by triple-quadrupole mass spectrometry. The quantitation was done under the matrix calibration curve using the external standard method. The results showed good linear relationships in the range of 5–200 ng/mL, and the correlation coefficient was greater than 0.999 in cosmetic samples. The limit of detection was in the range of 25–50 μg/kg and the limit of quantitation was in the range of 50–100 μg/kg. The recoveries of the method spiked ranged from 85.3% to 96.2% and the relative standard deviation (RSD) was in the range of 0.84%–2.08% (n = 6). The method is simple, quick, and accurate for the determination of L-ergothioneine in cosmetics, and has great practical value.

Does Lactobacillus reuteri influence ergothioneine levels in the human body?

The dietary thione-thiol, ergothioneine (ET), accumulates in human and animal tissues and may play important roles in disease prevention. ET biosynthesis has only been described in fungi and certain bacteria, and humans and animals are widely assumed to accumulate ET solely from diet. However, a recent study suggested that Lactobacillus/Limosilactobacillus reuteri, a commensal gut bacterium, may produce ET, thereby protecting the host against social defeat stress and sleep disturbances. Upon our further investigation, no evidence of ET biosynthesis was observed in L. reuteri when a heavy-labelled histidine precursor was administered. Instead, we discovered that L. reuteri avidly accumulates ET. This observation may indicate a possible mechanism by which the gut microbiota could influence tissue levels of ET in the host.

OCTN1: A Widely Studied but Still Enigmatic Organic Cation Transporter Linked to Human Pathology and Drug Interactions

The Novel Organic Cation Transporter, OCTN1, is the first member of the OCTN subfamily; it belongs to the wider Solute Carrier family SLC22, which counts many members including cation and anion organic transporters. The tertiary structure has not been resolved for any cation organic transporter. The functional role of OCNT1 is still not well assessed despite the many functional studies so far conducted. The lack of a definitive identification of OCTN1 function can be attributed to the different experimental systems and methodologies adopted for studying each of the proposed ligands. Apart from the contradictory data, the international scientific community agrees on a role of OCTN1 in protecting cells and tissues from oxidative and/or inflammatory damage. Moreover, the involvement of this transporter in drug interactions and delivery has been well clarified, even though the exact profile of the transported/interacting molecules is still somehow confusing. Therefore, OCTN1 continues to be a hot topic in terms of its functional role and structure. This review focuses on the most recent advances on OCTN1 in terms of functional aspects, physiological roles, substrate specificity, drug interactions, tissue expression, and relationships with pathology.

The role of SLC transporters for brain health and disease

The brain exchanges nutrients and small molecules with blood via the blood-brain barrier (BBB). Approximately 20% energy intake for the body is consumed by the brain. Glucose is known for its critical roles for energy production and provides substrates for biogenesis in neurons. The brain takes up glucose via glucose transporters GLUT1 and 3, which are expressed in several neural cell types. The brain is also equipped with various transport systems for acquiring amino acids, lactate, ketone bodies, lipids, and cofactors for neuronal functions. Unraveling the mechanisms by which the brain takes up and metabolizes these nutrients will be key in understanding the nutritional requirements in the brain. This could also offer opportunities for therapeutic interventions in several neurological disorders. For instance, emerging evidence suggests a critical role of lactate as an alternative energy source for neurons. Neuronal cells express monocarboxylic transporters to acquire lactate. As such, treatment of GLUT1-deficient patients with ketogenic diets to provide the brain with alternative sources of energy has been shown to improve the health of the patients. Many transporters are present in the brain, but only a small number has been characterized. In this review, we will discuss about the roles of solute carrier (SLC) transporters at the blood brain barrier (BBB) and neural cells, in transport of nutrients and metabolites in the brain.

The Ergothioneine Transporter (ETT): Substrates and Locations, an Inventory

In all vertebrates including mammals, the ergothioneine transporter ETT (obsolete name OCTN1; human gene symbol SLC22A4) is a powerful and highly specific transporter for the uptake of ergothioneine (ET). ETT is not expressed ubiquitously and only cells with high ETT cell-surface levels can accumulate ET to high concentration. Without ETT, there is no uptake because the plasma membrane is essentially impermeable to this hydrophilic zwitterion. Here, we review the substrate specificity and localization of ETT, which is prominently expressed in neutrophils, monocytes/macrophages, and developing erythrocytes. Most sites of strong expression are conserved across species, but there are also major differences. In particular, we critically analyze the evidence for the expression of ETT in the brain as well as recent data suggesting that the transporter SLC22A15 may transport also ET. We conclude that, to date, ETT remains the only well-defined biomarker for intracellular ET activity. In humans, the ability to take up, distribute, and retain ET depends principally on this transporter.

Matching chemical properties to molecular biological activities opens a new perspective on L-ergothioneine

L-ergothioneine is a low-molecular weight natural product, the chemical structure of which comprises oxygen-, nitrogen- and sulfur-containing functional groups. This gives L-ergothioneine specific physicochemical properties and allows to better understanding its chemical reactivity, which is primarily due to the 2-thio-imidazole group. Here, I review how different modes of chemical reactivity account for the reported molecular biological activities of L-ergothioneine. By matching the physicochemical properties to the biological properties of L-ergothioneine, a new perspective of the function and the mode of action of this enigmatic molecule emerges into the limelight.

Low plasma ergothioneine levels are associated with neurodegeneration and cerebrovascular disease in dementia

Ergothioneine (ET) is a dietary amino-thione with strong antioxidant and cytoprotective properties and has possible therapeutic potential for neurodegenerative and vascular diseases. Decreased blood concentrations of ET have been found in patients with mild cognitive impairment, but its status in neurodegenerative and vascular dementias is currently unclear. To address this, a cross-sectional study was conducted on 496 participants, consisting of 88 with no cognitive impairment (NCI), 201 with cognitive impairment, no dementia (CIND) as well as 207 with dementia, of whom 160 have Alzheimer's Disease (AD) and 47 have vascular dementia. All subjects underwent blood-draw, neuropsychological assessments, as well as neuroimaging assessments of cerebrovascular diseases (CeVD) and brain atrophy. Plasma ET as well as its metabolite l-hercynine were measured using high sensitivity liquid chromatography tandem-mass spectrometry (LC-MS/MS). Plasma ET concentrations were lowest in dementia (p < 0.001 vs. NCI and CIND), with intermediate levels in CIND (p < 0.001 vs. NCI). A significant increase in l-hercynine to ET ratio was also observed in dementia (p < 0.01 vs. NCI). In multivariate models adjusted for demographic and vascular risk factors, lower levels of ET were significantly associated with dementia both with or without CeVD, while ET associations with CIND were significant only in the presence of CeVD. Furthermore, lower ET levels were also associated with white matter hyperintensities and brain atrophy markers (reduced global cortical thickness and hippocampal volumes). The incremental decreases in ET levels along the CIND-dementia clinical continuum suggest that low levels of ET are associated with disease severity and could be a potential biomarker for cognitive impairment. Deficiency of ET may contribute towards neurodegeneration- and CeVD-associated cognitive impairments, possibly via the exacerbation of oxidative stress in these conditions.

S-Methyl-L-Ergothioneine to L-Ergothioneine Ratio in Urine Is a Marker of Cystine Lithiasis in a Cystinuria Mouse Model

Cystinuria, a rare inherited aminoaciduria condition, is characterized by the hyperexcretion of cystine, ornithine, lysine, and arginine. Its main clinical manifestation is cystine stone formation in the urinary tract, being responsible for 1–2% total and 6–8% pediatric lithiasis. Cystinuria patients suffer from recurrent lithiasic episodes that might end in surgical interventions, progressive renal functional deterioration, and kidney loss. Cystinuria is monitored for the presence of urinary cystine stones by crystalluria, imaging techniques or urinary cystine capacity; all with limited predicting capabilities. We analyzed blood and urine levels of the natural antioxidant L-ergothioneine in a Type B cystinuria mouse model, and urine levels of its metabolic product S-methyl-L-ergothioneine, in both male and female mice at two different ages and with different lithiasic phenotype. Urinary levels of S-methyl-L-ergothioneine showed differences related to age, gender and lithiasic phenotype. Once normalized by L-ergothioneine to account for interindividual differences, the S-methyl-L-ergothioneine to L-ergothioneine urinary ratio discriminated between cystine lithiasic phenotypes. Urine S-methyl-L-ergothioneine to L-ergothioneine ratio could be easily determined in urine and, as being capable of discriminating between cystine lithiasis phenotypes, it could be used as a lithiasis biomarker in cystinuria patient management.

Ergothioneine, recent developments

There has been a recent surge of interest in the unique low molecular weight dietary thiol/thione, ergothioneine. This compound can accumulate at high levels in the body from diet and may play important physiological roles in human health and development, and possibly in prevention and treatment of disease. Blood levels of ergothioneine decline with age and onset of various diseases. Here we highlight recent advances in our knowledge of ergothioneine.

In Vitro Production of Ergothioneine Isotopologues

Ergothioneine is an emerging component of the redox homeostasis system in human cells and in microbial pathogens, such as Mycobacterium tuberculosis and Burkholderia pseudomallei. The synthesis of stable isotope-labeled ergothioneine derivatives may provide important tools for deciphering the distribution, function, and metabolism of this compound in vivo. We describe a general protocol for the production of ergothioneine isotopologues with programmable ² H, ¹⁵ N, ¹³ C, ³⁴ S, and ³³ S isotope labeling patterns. This enzyme-based approach makes efficient use of commercial isotope reagents and is also directly applicable to the synthesis of radio-isotopologues.

The biology of ergothioneine, an antioxidant nutraceutical

Ergothioneine (ERG) is an unusual thio-histidine betaine amino acid that has potent antioxidant activities. It is synthesised by a variety of microbes, especially fungi (including in mushroom fruiting bodies) and actinobacteria, but is not synthesised by plants and animals who acquire it via the soil and their diet, respectively. Animals have evolved a highly selective transporter for it, known as solute carrier family 22, member 4 (SLC22A4) in humans, signifying its importance, and ERG may even have the status of a vitamin. ERG accumulates differentially in various tissues, according to their expression of SLC22A4, favouring those such as erythrocytes that may be subject to oxidative stress. Mushroom or ERG consumption seems to provide significant prevention against oxidative stress in a large variety of systems. ERG seems to have strong cytoprotective status, and its concentration is lowered in a number of chronic inflammatory diseases. It has been passed as safe by regulatory agencies, and may have value as a nutraceutical and antioxidant more generally.

Reflections of an aging free radical

In this mini-reflection, I explain how during my doctoral work in a Botany Department I first became interested in H2O2 and later in my career in other reactive oxygen species, especially the role of "catalytic" iron and haem compounds (including leghaemoglobin) in promoting oxidative damage. The important roles that H2O2, other ROS and dietary plants play in respect to humans are discussed. I also review the roles of diet-derived antioxidants in relation to human disease, presenting reasons why clinical trials using high doses of natural antioxidants have generally given disappointing results. Iron chelators and ergothioneine are reviewed as potential cytoprotective agents with antioxidant properties that may be useful therapeutically. The discovery of ferroptosis may also lead to novel agents that can be used to treat certain diseases.

Is ergothioneine a 'longevity vitamin' limited in the American diet?

There is mounting evidence for the potential for the natural dietary antioxidant and anti-inflammatory amino acid l-Ergothioneine (ERGO) to prevent or mitigate chronic diseases of aging. This has led to the suggestion that it could be considered a 'longevity vitamin.' ERGO is produced in nature only by certain fungi and a few other microbes. Mushrooms are, by far, the leading dietary source of ERGO, but it is found in small amounts throughout the food chain, most likely due to soil-borne fungi passing it on to plants. Because some common agricultural practices can disrupt beneficial fungus-plant root relationships, ERGO levels in foods grown under those conditions could be compromised. Thus, research is needed to further analyse the role agricultural practices play in the availability of ERGO in the human diet and its potential to improve our long-term health.

Effect of Ergothioneine on 7-Ketocholesterol-Induced Endothelial Injury

Ergothioneine (ET) is a naturally occurring antioxidant that is synthesized by non-yeast fungi and certain bacteria. ET is not synthesized by animals, including humans, but is avidly taken up from the diet, especially from mushrooms. In the current study, we elucidated the effect of ET on the hCMEC/D3 human brain endothelial cell line. Endothelial cells are exposed to high levels of the cholesterol oxidation product, 7-ketocholesterol (7KC), in patients with cardiovascular disease and diabetes, and this process is thought to mediate pathological inflammation. 7KC induces a dose-dependent loss of cell viability and an increase in apoptosis and necrosis in the endothelial cells. A relocalization of the tight junction proteins, zonula occludens-1 (ZO-1) and claudin-5, towards the nucleus of the cells was also observed. These effects were significantly attenuated by ET. In addition, 7KC induces marked increases in the mRNA expression of pro-inflammatory cytokines, IL-1β IL-6, IL-8, TNF-α and cyclooxygenase-2 (COX2), as well as COX2 enzymatic activity, and these were significantly reduced by ET. Moreover, the cytoprotective and anti-inflammatory effects of ET were significantly reduced by co-incubation with an inhibitor of the ET transporter, OCTN1 (VHCL). This shows that ET needs to enter the endothelial cells to have a protective effect and is unlikely to act via extracellular neutralizing of 7KC. The protective effect on inflammation in brain endothelial cells suggests that ET might be useful as a nutraceutical for the prevention or management of neurovascular diseases, such as stroke and vascular dementia. Moreover, the ability of ET to cross the blood-brain barrier could point to its usefulness in combatting 7KC that is produced in the CNS during neuroinflammation, e.g. after excitotoxicity, in chronic neurodegenerative diseases, and possibly COVID-19-related neurologic complications.

Could Ergothioneine Aid in the Treatment of Coronavirus Patients?

Infection with SARS-CoV-2 causes the coronavirus infectious disease 2019 (COVID-19), a pandemic that has, at present, infected more than 11 million people globally. Some COVID-19 patients develop a severe and critical illness, spurred on by excessive inflammation that can lead to respiratory or multiorgan failure. Numerous studies have established the unique array of cytoprotective properties of the dietary amino acid ergothioneine. Based on studies in a range of in vitro and in vivo models, ergothioneine has exhibited the ability to modulate inflammation, scavenge free radicals, protect against acute respiratory distress syndrome, prevent endothelial dysfunction, protect against ischemia and reperfusion injury, protect against neuronal damage, counteract iron dysregulation, hinder lung and liver fibrosis, and mitigate damage to the lungs, kidneys, liver, gastrointestinal tract, and testis, amongst many others. When compiled, this evidence suggests that ergothioneine has a potential application in the treatment of the underlying pathology of COVID-19. We propose that ergothioneine could be used as a therapeutic to reduce the severity and mortality of COVID-19, especially in the elderly and those with underlying health conditions. This review presents evidence to support that proposal.