Ergothioneine as antioxidant

Ergothioneine Protects Against UV-Induced Oxidative Stress Through the PI3K/AKT/Nrf2 Signaling Pathway

Background

Ergothioneine (EGT) is an antioxidant, which could be detected in human tissues, and human skin cells could utilize EGT and play an anti-oxidative role in keratinocytes. And in this study we are going to elucidate whether EGT could protect the skin from photoaging by Ultraviolet (UV) exposure in mice and its molecule pathway.

Methods

Histological analysis was performed for evaluating the skin structure change. Malondialdehyde (MDA) and superoxide dismutase (SOD) levels were measured with biological assay for evaluating oxidative and antioxidative ability of skin exposed to UV light. And the level of marker molecules in mouse skin were detected by hydroxyproline (Hyp) assay, immunohistochemical analysis, Western blot, and quantitative real-time PCR (qRT-PCR). The markers of skin aging and cell death were tested by cell culture and treatment, Western blot and qRT-PCR.

Results

EGT decreased the levels of inflammatory factors induced by UV exposure in mouse skin. MDA and SOD activity detection showed that EGT decreased MDA levels, increased SOD activity, and upregulated PI3K/Akt/Nrf2 signals in mouse skin exposed to UV, which further activated Nrf2 in the nucleus and enhanced the expression of Nrf2 target genes. In the cell model, we revealed that EGT could inhibit the increase in senescence-associated β-galactosidase-positive cells and p16 and γ-H2A.X positive cells induced by etoposide and activate PI3K/Akt/Nrf2 signaling. Moreover, a PI3K inhibitor blocked EGT protection against etoposide-induced cell death.

Conclusion

The study showed EGT may play an important protective role against cell damage or death through the PI3K/Akt/Nrf2 signaling pathway in skin.

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.

Biochemical and Structural Characterization of OvoATh2: A Mononuclear Nonheme Iron Enzyme from Hydrogenimonas thermophila for Ovothiol Biosynthesis

Ovothiol A and ergothioneine are thiol-histidine derivatives with sulfur substitutions at the δ-carbon or ε-carbon of the l-histidine imidazole ring, respectively. Both ovothiol A and ergothioneine have protective effects on many aging-related diseases, and the sulfur substitution plays a key role in determining their chemical and biological properties, while factors governing sulfur incorporation regioselectivities in ovothiol and ergothioneine biosynthesis in the corresponding enzymes (OvoA, Egt1, or EgtB) are not yet known. In this study, we have successfully obtained the first OvoA crystal structure, which provides critical information to explain their C-S bond formation regioselectivity. Furthermore, OvoATh2 exhibits several additional activities: (1) ergothioneine sulfoxide synthase activity akin to Egt1 in ergothioneine biosynthesis; (2) cysteine dioxygenase activity using l-cysteine and l-histidine analogues as substrates; (3) cysteine dioxygenase activity upon mutation of an active site tyrosine residue (Y406). The structural insights and diverse chemistries demonstrated by OvoATh2 pave the way for future comprehensive structure-function correlation studies.

Superior Photoprotection of Cyanine Dyes with Thio-imidazole Amino Acids

Preventing fluorophore photobleaching and unwanted blinking is crucial for single-molecule fluorescence (SMF) studies. Reductants achieve photoprotection via quenching excited triplet states, yet either require counteragents or, for popular alkyl-thiols, are limited to cyanine dye Cy3 protection. Here, we provide mechanistic and imaging results showing that the naturally occurring amino acid ergothioneine and its analogue dramatically enhance photostability for Cy3, Cy5, and their conformationally restrained congeners, providing a biocompatible universal solution for demanding fluorescence imaging.

Emerging roles of low-molecular-weight thiols at the host-microbe interface

Low-molecular-weight (LMW) thiols are an abundant class of cysteine-derived small molecules found in all forms of life that maintain reducing conditions within cells. While their contributions to cellular redox homeostasis are well established, LMW thiols can also mediate other aspects of cellular physiology, including intercellular interactions between microbial and host cells. Here we discuss emerging roles for these redox-active metabolites at the host-microbe interface. We begin by providing an overview of chemical and computational approaches to LMW-thiol discovery. Next, we highlight mechanisms of virulence regulation by LMW thiols in infected cells. Finally, we describe how microbial metabolism of these compounds may influence host physiology.

L-ergothioneine reduces nitration of lactoferrin and loss of antibacterial activity associated with nitrosative stress

Lactoferrin (LF) is a multifunctional antimicrobial, anti-inflammatory, and antioxidant protein that occurs naturally in mammals, most notably in exocrine gland tissues and fluids, such as in the eye. Nitrosative stress can promote changes to tyrosine and other amino acid residues of the protein, which also reduces the activity of LF. l-ergothioneine (ET) is a potent anti-inflammatory antioxidant present in the eye and other tissues through nutrition or supplementation and that may play a role in the prevention or treatment of a variety of diseases. Here we investigated the ability of ET to reduce 3-nitrotyrosine (NTyr) formation using two separate substrates, with the goal of determining whether ET can protect the antibacterial function of LF and other proteins when exposed separately to peroxynitrite and tetranitromethane as nitrating reagents. Native human LF was used as a simple protein substrate, and lamb corneal lysate was chosen as one example of mammalian tissue with a more complex mixture of proteins and other biomolecules. Nitration was monitored by absorbance and fluorescence spectroscopy as well as sandwich (nitrated LF) and direct NTyr (corneal lysate) enzyme-linked immunosorbent assays (ELISAs). We found that pretreatment with ET reduced chemical modification of both native LF and corneal lysate samples and loss of antibacterial LF function due to exposure to the nitrating reagents. These initial results suggest that ET, raised to sufficiently elevated levels, could be tailored as a therapeutic agent to reduce effects of nitrosative stress on LF and in turn sustain the protein activity.

Characterization of hydantoin-5-propionic acid amidohydrolase involved in ergothioneine utilization in Burkholderia sp. HME13

In our previous study, ertABC genes encoding ergothionase, thiourocanate hydratase, and 3-(5-oxo-2-thioxoimidazolidin-4-yl) propionic acid desulfhydrase were identified, all of which may be involved in ergothioneine utilization of Burkholderia sp. HME13. In this study, we identify the ertD gene encoding metal-dependent hydantoin-5-propionic acid amidohydrolase in this strain. Mn2+-containing ErtD showed maximum activity at 45 °C and pH 8.5 and was stable at temperatures up to 45 °C. The Km and Vmax values of Mn2+-containing ErtD for hydantoin-5-propionic acid were 2.8 m m and 16 U/mg, respectively. Real-time polymerase chain reaction (PCR) revealed that ertD expression levels in Burkholderia sp. HME13 cells cultivated in ergothioneine medium were 3.3-fold higher than those in cells cultivated in Luria-Bertani (LB) medium. ErtD activity in the crude extract from Burkholderia sp. HME13 cells cultured in ergothioneine medium was 0.018 U/mg, whereas that in LB medium was not detected. Accordingly, we suggest that ErtD is involved in ergothioneine utilization in this strain.

Ergothioneine: new functional factor in fermented foods

Ergothioneine (EGT) is a high-value natural sulfur-containing amino acid and has been shown to possess extremely potent antioxidant and cytoprotective activities. At present, EGT has been widely used in food, functional food, cosmetics, medicine, and other industries, but its low yield is still an urgent problem to overcome. This review briefly introduced the biological activities and functions of EGT, and expounded its specific applications in food, functional food, cosmetic, and medical industries, introduced and compared the main production methods of EGT and respective biosynthetic pathways in different microorganisms. Furthermore, the use of genetic and metabolic engineering methods to improve EGT production was discussed. In addition, the incorporation of some food-derived EGT-producing strains into fermentation process will allow the EGT to act as a new functional factor in the fermented foods.

Ergothioneine attenuates varicocele-induced testicular damage by upregulating HSP90AA1 in rats

This study investigates the therapeutic effect and the underlying mechanisms of ergothioneine (EGT) on the testicular damage caused by varicocele (VC) in vivo, in vitro, and in silico. This preclinical study combines a series of biological experiments and network pharmacology analyses. A total of 18 Sprague Dawley (SD) male rats were randomly and averagely divided into three groups: the sham-operated, VC model, and VC model with EGT treatment (VC + EGT) groups. The left renal vein of the VC model and the VC + EGT groups were half-ligated for 4 weeks. Meanwhile, the VC + EGT group was intragastrically administrated with EGT (10 mg/kg). GC1 and GC2 cells were exposed to H₂ O₂ with or without EGT treatment to re-verify the conclusion. The structure disorder of seminiferous tubules ameliorated the apoptosis decrease in the VC rats receiving EGT. EGT can also increase the sperm quality of the VC model rats (p < 0.05). The exposure to H₂ O₂ decreased proliferation and increased apoptosis of GC1 and GC2 cells, which was revisable by adding EGT to the plates (p < 0.05). The network pharmacology and molecular docking were conducted to explore the potential targets of EGT in VC, and HSP90AA1 was identified as the pivotal gene, which was validated by western blot, immunohistochemistry, and RT-qPCR both in vivo and in vitro (p < 0.05). Overall, EGT attenuates the testicular injury in the VC model both in vivo and in vitro by potentially potentiating the expression of HSP90AA1.

Discovery and structure of a widespread bacterial ABC transporter specific for ergothioneine

L-Ergothioneine (ET), the 2-thioimidazole derivative of trimethylhistidine, is biosynthesized by select fungi and bacteria, notably Mycobacterium tuberculosis, and functions as a scavenger of reactive oxygen species. The extent to which ET broadly functions in bacterial cells unable to synthesize it is unknown. Here we show that spd_1642-1643 in Streptococcus pneumoniae, a Gram-positive respiratory pathogen, encodes an ET uptake ATP-binding cassette (ABC) transporter, designated EgtU. The solute binding domain (SBD) of EgtU, EgtUC, binds ET with high affinity and exquisite specificity in a cleft between the two subdomains, with cation-π interactions engaging the betaine moiety and a network of water molecules that surround the thioimidazole ring. EgtU is highly conserved among known quaternary amine compound-specific transporters and widely distributed in Firmicutes, including the human pathogens Listeria monocytogenes, as BilEB, Enterococcus faecalis and Staphylococcus aureus. ET increases the chemical diversity of the low molecular weight thiol pool in Gram-positive human pathogens and may contribute to antioxidant defenses in the infected host.

Ergothioneine and its prospects as an anti-ageing compound

Healthy ageing is a crucial process that needs to be highlighted as it affects the quality of lifespan. An increase in oxidative stress along with ageing is the major factor related to the age-associated diseases, especially neurodegenerative disorders. An antioxidant-rich diet has been proven to play a significant role in the ageing process. Targeting ageing mechanisms could be a worthwhile approach to improving health standards. Ergothioneine (EGT), a hydrophilic compound with specific transporter known as OCTN1, has been shown to exert anti-ageing properties. In addition to its antioxidant effect, EGT has been reported to have anti-senescence, anti-inflammatory and anti-neurodegenerative properties. This review aims to define the pivotal role of EGT in major signalling pathways in ageing such as insulin/insulin-like growth factor (IGF) signalling (IIS), sirtuin 6 (SIRT6) and mammalian target of rapamycin complex (mTOR) pathways. The review further discusses evidence of EGT on neurodegeneration in its therapeutic context in various model organisms, providing new insights into improving health. In conclusion, an ergothioneine-rich diet may be beneficial in preventing age-related diseases, resulting in a healthy ageing population.

Integration of metagenomic and metabolomic insights into the effects of microcystin-LR on intestinal microbiota of Litopenaeus vannamei

Microcystin-LR (MC-LR) is a hazardous substance that threaten the health of aquatic animals. Intestinal microbes and their metabolites can interact with hosts to influence physiological homeostasis. In this study, the shrimp Litopenaeus vannamei were exposed to 1.0 μg/l MC-LR for 72 h, and the toxic effects of MC-LR on the intestinal microbial metagenomic and metabolomic responses of the shrimp were investigated. The results showed that MC-LR stress altered the gene functions of intestinal microbial, including ABC transporter, sulfur metabolism and riboflavin (VB2) metabolism, and induced a significant increase of eight carbohydrate metabolism enzymes. Alternatively, intestinal metabolic phenotypes were also altered, especially ABC transporters, protein digestion and absorption, and the biosynthesis and metabolism of amino acid. Furthermore, based on the integration of intestinal microbial metagenomic and metabolome, four bacteria species (Demequina globuliformis, Demequina sp. NBRC 110055, Sphingomonas taxi and Sphingomonas sp. RIT328) and three metabolites (yangonin, α-hederin and soyasaponin ii) biomarkers were identified. Overall, our study provides new insights into the effects of MC-LR on the intestinal microbial functions of L. vannamei.

Ergothioneine Production by Submerged Fermentation of a Medicinal Mushroom Panus conchatus

Ergothioneine is a natural and safe antioxidant that plays an important role in anti-aging and the prevention of various diseases. This study aimed to report on a kind of medicinal mushroom of Panus conchatus with great potential for the bioproduction of ergothioneine. The effect of different nutritional and environmental conditions on the growth of Panus conchatus and ergothioneine production were investigated. Molasses and soy peptone were found to promote cell growth of Panus conchatus and enhance ergothioneine accumulation. Adding precursors of histidine, methionine and cysteine could increase ergothioneine production and the highest ergothioneine concentration of 148.79 mg/L was obtained. Finally, the extraction and purification processes were also established to obtain the crude ergothioneine extract for further antioxidant property evaluation. The ergothioneine from Panus conchatus showed high antioxidant activity with good stability in a lower pH environment. This study provided a new strain and process for the bioproduction of ergothioneine.

Ergothioneine: A Stress Vitamin with Antiaging, Vascular, and Neuroprotective Roles?

Significance: Ergothioneine (ET) is an unusual sulfur-containing amino acid derived from histidine, acquired predominantly from food. Its depletion is associated with deleterious consequences in response to stress stimuli in cell culture models, prompting us to classify it as a vitamin in 2010, which was later supported by in vivo studies. ET is obtained from a variety of foods and is taken up by a selective transporter. ET possesses antioxidant and anti-inflammatory properties that confer cytoprotection. ET crosses the blood-brain barrier and has been reported to have beneficial effects in the brain. In this study, we discuss the cytoprotective and neuroprotective properties of ET, which may be harnessed for combating neurodegeneration and decline during aging. Recent Advances: The designation of ET as a stress vitamin is gaining momentum, opening a new field of investigation involving small molecules that are essential for optimal physiological functioning and maintenance of health span. Critical Issues: Although ET was discovered more than a century ago, its physiological functions are still being elucidated, especially in the brain. As ET is present in most foods, toxicity associated with its deprivation has been difficult to assess. Future Directions: Using genetically engineered cells and mice, it may now be possible to elucidate roles of ET. This coupled with advances in genomics and metabolomics may lead to identification of ET function. As ET is a stable antioxidant with anti-inflammatory properties, whose levels decline during aging, supplementing ET in the diet or consuming an ET-rich diet may prove beneficial. Antioxid. Redox Signal. 36, 1306-1317.

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.

Oxidized Forms of Ergothioneine Are Substrates for Mammalian Thioredoxin Reductase

Ergothioneine (EGT) is a sulfur-containing amino acid analog that is biosynthesized in fungi and bacteria, accumulated in plants, and ingested by humans where it is concentrated in tissues under oxidative stress. While the physiological function of EGT is not yet fully understood, EGT is a potent antioxidant in vitro. Here we report that oxidized forms of EGT, EGT-disulfide (ESSE) and 5-oxo-EGT, can be reduced by the selenoenzyme mammalian thioredoxin reductase (Sec-TrxR). ESSE and 5-oxo-EGT are formed upon reaction with biologically relevant reactive oxygen species. We found that glutathione reductase (GR) can reduce ESSE, but only with the aid of glutathione (GSH). The reduction of ESSE by TrxR was found to be selenium dependent, with non-selenium-containing TrxR enzymes having little or no ability to reduce ESSE. In comparing the reduction of ESSE by Sec-TrxR in the presence of thioredoxin to that of GR/GSH, we find that the glutathione system is 10-fold more efficient, but Sec-TrxR has the advantage of being able to reduce both ESSE and 5-oxo-EGT directly. This represents the first discovered direct enzymatic recycling system for oxidized forms of EGT. Based on our in vitro results, the thioredoxin system may be important for EGT redox biology and requires further in vivo investigation.

Ergothioneine: a potential antioxidative and anti-melanosis agent for food quality preservation

The global population increase has increased the demand for food products. However, post-harvest deterioration due to oxidation and discoloration results in a drastic loss of food quality and supply. Thus, research has focused on developing strategies to minimize such losses. One of those strategies includes the application of ergothioneine (ET), a potent hydrophilic antioxidant, to several food products so as to overcome their short shelf-life. ET can be synthetic or derived from several species of edible mushrooms and their extracts, which are known sources of natural ET. Given the reported potential of ET in food quality preservation, this review compiles the recent applications of ET as a preservative for maintaining the quality of food commodities.

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.

Discovery of donor age markers from bloodstain by LC-MS/MS using a metabolic approach

Bloodstains are frequently encountered at crime scenes and they provide important evidence about the incident, such as information about the victim or suspect and the time of death or other events. Efforts have been made to identify the age of the bloodstain's donor through genomic approaches, but there are some limitations, such as the availability of databases and the quality dependence of DNA. There is a need for the development of a tool that can obtain information at once from a small blood sample. The aim of this study is to identify bloodstain metabolite candidates that can be used to determine donor age. We prepared bloodstain samples and analyzed metabolites using high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). Eighteen molecular features (MFs) were selected as candidates using volcano plots and multivariate analysis. Based on the MS/MS spectrum of the MFs, the following nine metabolites were identified from the METaboliteLINk database: Δ2-cis eicosenoic acid, ergothioneine, adenosine 5'-monophosphate, benzaldehyde, phenacylamine, myristic acid ethyl ester, p-coumaric acid, niacinamide, and N-arachidonoyl-L-alanine. These nine age markers at high or low abundances could be used to estimate the age of a bloodstain's donor. This study was the first to develop metabolite age markers that can be used to analyze crime scene bloodstains.

Ergothioneine in a peptide: Substitution of histidine with 2-thiohistidine in bioactive peptides

Ergothioneine (EGT) is the betaine of 2-thiohistidine (2-thioHis) and may be the last undiscovered vitamin. EGT cannot be incorporated into a peptide because the α-nitrogen is trimethylated, although this would be advantageous as an EGT-like moiety in a peptide would impart unique antioxidant and metal chelation properties. The amino acid 2-thioHis is an analogue of EGT and can be incorporated into a peptide, although there is only one reported occurrence of this in the literature. A likely reason is the harsh conditions reported for protection of the thione, with similarly harsh conditions used in order to achieve deprotection after synthesis. Here, we report a novel strategy for the incorporation of 2-thioHis into peptides in which we decided to leave the thione unprotected. This decision was based upon the reported low reactivity of EGT with 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), a very electrophilic disulfide. This strategy was successful, and we report here the synthesis of 2-thioHis analogues of carnosine (βAH), GHK-tripeptide, and HGPLGPL. Each of these peptides contain a histidine (His) residue and possesses biological activity. Our results show that substitution of His with 2-thioHis imparts strong antioxidant, radical scavenging, and copper binding properties to the peptide. Notably, we found that the 2-thioHis analogue of GHK-tripeptide was able to completely quench the hydroxyl and ABTS radicals in our assays, and its antioxidant capacity was significantly greater than would be expected based on the antioxidant capacity of free 2-thioHis. Our work makes possible greater future use of 2-thioHis in peptides.

Effects of ergothioneine-enriched mushroom extract on oxidative stability, volatile compounds and sensory quality of emulsified sausage

Objective

The aim of this work was to assess the effect of ergothioneine (ESH)-enriched mushroom extract on oxidative stability, volatile compounds, and sensory quality of emulsified sausage.

Methods

The ESH content was determined by high performance liquid chromatography. The antioxidant activity of Flammulina velutipes (F. velutipes) extract was determined through radical-scavenging activity of 1,1 diphenyl-2-picryl-hydrazyl, 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) and hydroxyl radicals. Four different groups of emulsified sausage were manufactured: control, no antioxidants; BHA, 0.01% butylated hydroxyanisole; EEME, 0.8% ESH-enriched mushroom (F. velutipes) extract; AE, 0.012% authentic ESH, after storage for 14 days (at 4°C), the quality of sausage including oxidative stability (2-thiobarbituric acid reactive substances and protein carbonyls content), volatile compounds and sensory quality were studied.

Results

It was demonstrated that adding ESH-enriched F. velutipes extract to sausage could effectively prevent lipid and protein oxidation, and its efficacy was equivalent with 0.01% BHA. During meat processing, the ESH mainly contributed to the antioxidative activity of F. velutipes extract. The flavor and sensory attributes of emulsified sausage were improved through adding ESH-enriched F. velutipes extract.

Conclusion

Accordingly, the extract of F. velutipes contained high-level of ESH and could be a good antioxidant candidate for processed meat production.

Identification of the gene encoding 3-(5-oxo-2-thioxoimidazolidin-4-yl) propionic acid desulfhydrase in Burkholderia sp. HME13

Here, we report the identification of the gene encoding a novel enzyme, 3-(5-oxo-2-thioxoimidazolidin-4-yl) propionic acid desulfhydrase, in Burkholderia sp. HME13. The enzyme converts 3-(5-oxo-2-thioxoimidazolidin-4-yl) propionic acid and H2O to 3-(2,5-dioxoimidazolidin-4-yl) propionic acid and H2S. Amino acid sequence analysis of the enzyme indicates that it belongs to the DUF917 protein family, which consists of proteins of unknown function.

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.

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.

Successful biosynthesis of natural antioxidant ergothioneine in Saccharomyces cerevisiae required only two genes from Grifola frondosa

Background

Ergothioneine (EGT) has a unique antioxidant ability and diverse beneficial effects on human health. But the content of EGT is very low in its natural producing organisms such as Mycobacterium smegmatis and mushrooms. Therefore, it is necessary to highly efficient heterologous production of EGT in food-grade yeasts such as Saccharomyces cerevisiae.

Results

Two EGT biosynthetic genes were cloned from the mushroom Grifola frondosa and successfully heterologously expressed in Saccharomyces cerevisiae EC1118 strain in this study. By optimization of the fermentation conditions of the engineered strain S. cerevisiae EC1118, the 11.80 mg/L of EGT production was obtained. With daily addition of 1% glycerol to the culture medium in the fermentation process, the EGT production of the engineered strain S. cerevisiae EC1118 can reach up to 20.61 mg/L.

Conclusion

A successful EGT de novo biosynthetic system of S. cerevisiae containing only two genes from mushroom Grifola frondosa was developed in this study. This system provides promising prospects for the large scales production of EGT for human health.

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.

Involvement of Sulfur in the Biosynthesis of Essential Metabolites in Pathogenic Fungi of Animals, Particularly Aspergillus spp.: Molecular and Therapeutic Implications

Fungal sulfur uptake is required for incorporation into the sidechains of the amino acids cysteine and methionine, and is also essential for the biosynthesis of the antioxidant glutathione (GSH), S-adenosylmethionine (SAM), the key source of methyl groups in cellular transmethylation reactions, and S-adenosylhomocysteine (SAH). Biosynthesis of redox-active gliotoxin in the opportunistic fungal pathogen Aspergillus fumigatus has been elucidated over the past 10 years. Some fungi which produce gliotoxin-like molecular species have undergone unexpected molecular rewiring to accommodate this high-risk biosynthetic process. Specific disruption of gliotoxin biosynthesis, via deletion of gliK, which encodes a γ-glutamyl cyclotransferase, leads to elevated intracellular antioxidant, ergothioneine (EGT), levels, and confirms crosstalk between the biosynthesis of both sulfur-containing moieties. Gliotoxin is ultimately formed by gliotoxin oxidoreductase GliT-mediated oxidation of dithiol gliotoxin (DTG). In fact, DTG is a substrate for both GliT and a bis-thiomethyltransferase, GtmA. GtmA converts DTG to bisdethiobis(methylthio)gliotoxin (BmGT), using 2 mol SAM and resultant SAH must be re-converted to SAM via the action of the Methyl/Met cycle. In the absence of GliT, DTG fluxes via GtmA to BmGT, which results in both SAM depletion and SAH overproduction. Thus, the negative regulation of gliotoxin biosynthesis via GtmA must be counter-balanced by GliT activity to avoid Methyl/Met cycle dysregulation, SAM depletion and trans consequences on global cellular biochemistry in A. fumigatus. DTG also possesses potent Zn²⁺ chelation properties which positions this sulfur-containing metabolite as a putative component of the Zn²⁺ homeostasis system within fungi. EGT plays an essential role in high-level redox homeostasis and its presence requires significant consideration in future oxidative stress studies in pathogenic filamentous fungi. In certain filamentous fungi, sulfur is additionally indirectly required for the formation of EGT and the disulfide-bridge containing non-ribosomal peptide, gliotoxin, and related epipolythiodioxopiperazines. Ultimately, interference with emerging sulfur metabolite functionality may represent a new strategy for antifungal drug development.

Gene cloning and characterization of thiourocanate hydratase from Burkholderia sp. HME13

A novel enzyme, thiourocanate hydratase, which catalyses the conversion of thiourocanic acid to 3-(5-oxo-2-thioxoimidazolidin-4-yl) propionic acid, was isolated from the ergothioneine-utilizing strain, Burkholderia sp. HME13. When the HME13 cells were cultured in medium containing ergothioneine as the sole nitrogen source, thiourocanate-metabolizing activity was detected in the crude extract from the cells. However, activity was not detected in the crude extract from HME13 cells that were cultured in Luria-Bertani medium. The gene encoding thiourocanate hydratase was cloned and expressed in Escherichia coli, and the recombinant enzyme was purified to homogeneity. The enzyme showed maximum activity at pH 7.5 and 55°C and was stable between pH 5.0 and 10.5, and at temperatures up to 45°C. The Km and Vmax values of thiourocanate hydratase towards thiourocanic acid were 30 μM and 7.1 μmol/min/mg, respectively. The enzyme was strongly inhibited by CuCl2 and HgCl2. The amino acid sequence of the enzyme showed 46% identity to urocanase from Pseudomonas putida, but thiourocanate hydratase had no urocanase activity.

Ab initio molecular dynamics of free radical-induced oxidation of ergothioneine

Ergothioneine (2-mercaptohistidine trimethylbetaine) is a very stable natural compound largely present in cells and tissues of plants and mammals. The biological role of ET is still incompletely understood but its antioxidant properties are well assessed experimentally. However, no theoretical study had been performed until now to analyze the first steps of the reactions between this natural compound and strong oxidants in order to gain more knowledge on the reaction mechanisms. In this paper, the reaction of ergothioneine with two strong oxidants, hydroxyl radical and peroxinitrite, is modeled in a cluster of forty to fifty water molecules by ab-initio molecular dynamics. The reaction of hydroxyl radical with ergothioneine consists in electron transfer. When hydroxyl radical is initially situated near the sulfur atom, the reaction is not barrier less but passes through a transition state formed by a strong adduct. Otherwise, the charge transfer occurs when the two reactants and a "wire" of water molecules form a loop allowing the charge flow.

Non-heme iron enzyme-catalyzed complex transformations: Endoperoxidation, cyclopropanation, orthoester, oxidative C-C and C-S bond formation reactions in natural product biosynthesis

Non-heme iron enzymes catalyze a wide range of chemical transformations, serving as one of the key types of tailoring enzymes in the biosynthesis of natural products. Hydroxylation reaction is the most common type of reactions catalyzed by these enzymes and hydroxylation reactions have been extensively investigated mechanistically. However, the mechanistic details for other types of transformations remain largely unknown or unexplored. In this paper, we present some of the most recently discovered transformations, including endoperoxidation, orthoester formation, cyclopropanation, oxidative C-C and C-S bond formation reactions. In addition, many of them are multi-functional enzymes, which further complicate their mechanistic investigations. In this work, we summarize their biosynthetic pathways, with special emphasis on the mechanistic details available for these newly discovered enzymes.

Crystal Structure of the Ergothioneine Sulfoxide Synthase from Candidatus Chloracidobacterium thermophilum and Structure-Guided Engineering To Modulate Its Substrate Selectivity

Ergothioneine is a thiohistidine derivative with potential benefits on many aging-related diseases. The central step of aerobic ergothioneine biosynthesis is the oxidative C-S bond formation reaction catalyzed by mononuclear nonheme iron sulfoxide synthases (EgtB and Egt1). Thus far, only the Mycobacterium thermoresistibile EgtB (EgtB _Mth ) crystal structure is available, while the structural information for the more industrially attractive Egt1 enzyme is not. Herein, we reported the crystal structure of the ergothioneine sulfoxide synthase (EgtB _Cth ) from Candidatus Chloracidobacterium thermophilum. EgtB _Cth has both EgtB- and Egt1-type of activities. Guided by the structural information, we conducted Rosetta Enzyme Design calculations, and we biochemically demonstrated that EgtB _Cth can be engineered more toward Egt1-type of activity. This study provides information regarding the factors governing the substrate selectivity in Egt1- and EgtB-catalysis and lays the groundwork for future sulfoxide synthase engineering toward the development of an effective ergothioneine process through a synthetic biology approach.

Effects of Ergothioneine-Rich Mushroom Extract on the Oxidative Stability of Astaxanthin in Liposomes

Ergothioneine-rich crude extracts of Pleurotus cornucopiae were used as a source of antioxidative components to control the effects of lipid oxidation in astaxanthin-containing liposomes. This study aimed to elucidate the interactions of liposomal astaxanthin and lipids with ergothioneine-rich mushroom extract (ME) under radical oxidation-induced conditions to provide a better understanding of the agricultural and postharvest applications of this strategy. Azo compounds (2,2'-azobis(2-methylpropionamidine) dihydrochloride and 2,2'-azobis(2,4-dimethylvaleronitrile) were used as hydrophilic and lipophilic radical initiators, respectively. Results of this study demonstrate that the presence of ME significantly delayed the oxidative degradation of astaxanthin and controlled the progress of lipid oxidation in a liposomal system. The lipid hydroperoxide formation was significantly suppressed, while polyunsaturated fatty acids were protected from degradation. In addition, Crude ME also demonstrated more potent DPPH radical scavenging activities and EC₅₀ than the equimolar concentrations of ergothioneine alone, which suggested the presence of additional compounds with antioxidative properties.

Prolonging healthy aging: Longevity vitamins and proteins

It is proposed that proteins/enzymes be classified into two classes according to their essentiality for immediate survival/reproduction and their function in long-term health: that is, survival proteins versus longevity proteins. As proposed by the triage theory, a modest deficiency of one of the nutrients/cofactors triggers a built-in rationing mechanism that favors the proteins needed for immediate survival and reproduction (survival proteins) while sacrificing those needed to protect against future damage (longevity proteins). Impairment of the function of longevity proteins results in an insidious acceleration of the risk of diseases associated with aging. I also propose that nutrients required for the function of longevity proteins constitute a class of vitamins that are here named "longevity vitamins." I suggest that many such nutrients play a dual role for both survival and longevity. The evidence for classifying taurine as a conditional vitamin, and the following 10 compounds as putative longevity vitamins, is reviewed: the fungal antioxidant ergothioneine; the bacterial metabolites pyrroloquinoline quinone (PQQ) and queuine; and the plant antioxidant carotenoids lutein, zeaxanthin, lycopene, α- and β-carotene, β-cryptoxanthin, and the marine carotenoid astaxanthin. Because nutrient deficiencies are highly prevalent in the United States (and elsewhere), appropriate supplementation and/or an improved diet could reduce much of the consequent risk of chronic disease and premature aging.

Ergothioneine production with Aspergillus oryzae

To establish a reliable and practical ergothioneine (ERG) supply, we employed fermentative ERG production using Aspergillus oryzae, a fungus used for food production. We heterologously overexpressed the egt-1 and -2 genes of Neurospora crassa in A. oryzae and succeeded in producing ERG (231.0 mg/kg of media, which was 20 times higher than the wild type). Abbreviations: ERG: ergothioneine; HER: hercynine; Cys-HER: hercynylcysteine-sulfoxide; SAM: S-adenosylmethionine; SAH: S-adenosylhomocysteine; l-His: l-histidine; l-Cys: l-cysteine; LC-ESI-MS: liquid chromatography-electrospray ionization-mass spectrometry.

Ergothioneine prevents endothelial dysfunction induced by mercury chloride

Exposure to mercury has detrimental effects on the cardiovascular system, particularly the vascular endothelium. The present study aimed to investigate the effects of ergothioneine (EGT) on endothelial dysfunction induced by low-dose mercury chloride (HgCl₂). Agonist-induced contractions and relaxations were evaluated in isolated aortic rings from 3-month-old male Wistar rats treated by intra-muscular injection to caudal hind leg muscle with HgCl₂ (first dose, 4.6 µg/kg; subsequent doses, 0.07 µg/kg/day for 15 days) and optionally with EGT (2 µg/kg for 30 days). Reactive oxygen species (ROS) in aortic rings were measured by means of lucigenin- and luminol-enhanced chemiluminescence. The protein level of endothelial nitric oxide synthase was evaluated by ELISA. Blood glutathione (GSH) and catalase levels, lipid peroxidation and total nitrite were measured spectrophotometrically. The results indicated that low-dose HgCl₂ administration impaired acetylcholine (ACh)-induced relaxation and potentiated phenylephrine- and serotonin-induced contractions in rat aortas. In addition, HgCl₂ significantly increased the levels of ROS in the aortic tissue. EGT prevented the loss of ACh-induced relaxations and the increase in contractile responses. These effects were accompanied by a significant decrease in ROS levels. EGT also improved the ratio of reduced GSH to oxidized GSH and catalase levels with a concomitant decrease in lipid peroxidation. In conclusion, to the best of our knowledge, the present study was the first to report that EGT prevents endothelial dysfunction induced by low-dose HgCl₂ administration. EGT may serve as a therapeutic tool to reduce mercury-associated cardiovascular complications via improving the antioxidant status.

Mini-Review: Ergothioneine and Ovothiol Biosyntheses, an Unprecedented Trans-Sulfur Strategy in Natural Product Biosynthesis

As one of the most abundant elements on earth, sulfur is part of many small molecular metabolites and is key to their biological activities. Over the past few decades, some general strategies have been discovered for the incorporation of sulfur into natural products. In this review, we summarize recent efforts in elucidating the biosynthetic details for two sulfur-containing metabolites, ergothioneine and ovothiol. Their biosyntheses involve an unprecedented trans-sulfur strategy, a combination of a mononuclear non-heme iron enzyme-catalyzed oxidative C-S bond formation reaction and a PLP enzyme-mediated C-S lyase reaction.

Substrate Selectivity Check of the Ergothioneine Transporter

The candidate vitamin ergothioneine (ET) is a unique antioxidant. Expression of the ET transporter (ETT) (gene symbol SLC22A4) in distinct cells is thought to signal intracellular ET activity, since we have previously shown that the ETT is highly selective for ET. Unfortunately, some continue to hold the ETT as a relevant drug transporter, using the misleading functional name OCTN1, novel organic cation transporter. The present study was provoked by two recent reports in which new ETT substrates were declared. Astonishingly, the transport efficiencies (TEs) of ETT for saracatinib and some nucleoside drugs were as high as the TE for ET. Here we examined, based on regulated expression of ETT from human and rat in 293 cells and liquid chromatography-mass spectrometry quantification, the transport of several drugs. With the nucleosides cytarabine, gemcitabine, 2'-deoxycytidine, and 2'-deoxyadenosine, and the drugs saracatinib, ipratropium, metformin, and oxaliplatin, the uptake into cells expressing ETT was not increased over control cells. ETT-mediated uptake of gabapentin was detectable, but the TE was approximately 100-fold lower than the TE for ergothioneine (50-200 µl/min per milligram of protein). In conclusion, the ETT remains highly specific for its physiologic substrate ergothioneine. Our results contradict several reports on additional substrates. The ETT does not provide multiple substrate specificities, and it is not a transporter of cationic drugs. Only compounds that are related to ET in substructure-for example, gabapentin, carnitine, and TEA-can be transported, but with very low efficiency. Thus, ETT persists as a specific molecular indicator of ET activity.

Role of Ergothioneine in Microbial Physiology and Pathogenesis

SIGNIFICANCE

L-ergothioneine is synthesized in actinomycetes, cyanobacteria, methylobacteria, and some fungi. In contrast to other low-molecular-weight redox buffers, glutathione and mycothiol, ergothioneine is primarily present as a thione rather than a thiol at physiological pH, which makes it resistant to autoxidation. Ergothioneine regulates microbial physiology and enables the survival of microbes under stressful conditions encountered in their natural environments. In particular, ergothioneine enables pathogenic microbes, such as Mycobacterium tuberculosis (Mtb), to withstand hostile environments within the host to establish infection. Recent Advances: Ergothioneine has been reported to maintain bioenergetic homeostasis in Mtb and protect Mtb against oxidative stresses, thereby enhancing the virulence of Mtb in a mouse model. Furthermore, ergothioneine augments the resistance of Mtb to current frontline anti-TB drugs. Recently, an opportunistic fungus, Aspergillus fumigatus, which infects immunocompromised individuals, has been found to produce ergothioneine, which is important in conidial health and germination, and contributes to the fungal resistance against redox stresses.

CRITICAL ISSUES

The molecular mechanisms of the functions of ergothioneine in microbial physiology and pathogenesis are poorly understood. It is currently not known if ergothioneine is used in detoxification or antioxidant enzymatic pathways. As ergothioneine is involved in bioenergetic and redox homeostasis and antibiotic susceptibility of Mtb, it is of utmost importance to advance our understanding of these mechanisms.

FUTURE DIRECTIONS

A clear understanding of the role of ergothioneine in microbes will advance our knowledge of how this thione enhances microbial virulence and resistance to the host's defense mechanisms to avoid complete eradication. Antioxid. Redox Signal. 28, 431-444.

Mushrooms: A rich source of the antioxidants ergothioneine and glutathione

While mushrooms are the highest dietary source for the unique sulfur-containing antioxidant ergothioneine, little is known regarding levels of the major biological antioxidant glutathione. Thus, our objectives were to determine and compare levels of glutathione, as well as ergothioneine, in different species of mushrooms. Glutathione levels varied >20-fold (0.11-2.41mg/gdw) with some varieties having higher levels than reported for other foods. Ergothioneine levels also varied widely (0.15-7.27mg/gdw) and were highly correlated with those of glutathione (r=0.62, P<0.001). Both antioxidants were more concentrated in pileus than stipe tissues in selected mushrooms species. Agaricus bisporus harvested during the third cropping flush contained higher levels of ergothioneine and glutathione compared to the first flush, possibly as a response to increased oxidative stress. This study demonstrated that certain mushroom species are high in glutathione and ergothioneine and should be considered an excellent dietary source of these important antioxidants.

Enzymatic Carbon-Sulfur Bond Formation in Natural Product Biosynthesis

Sulfur plays a critical role for the development and maintenance of life on earth, which is reflected by the wealth of primary metabolites, macromolecules, and cofactors bearing this element. Whereas a large body of knowledge has existed for sulfur trafficking in primary metabolism, the secondary metabolism involving sulfur has long been neglected. Yet, diverse sulfur functionalities have a major impact on the biological activities of natural products. Recent research at the genetic, biochemical, and chemical levels has unearthed a broad range of enzymes, sulfur shuttles, and chemical mechanisms for generating carbon-sulfur bonds. This Review will give the first systematic overview on enzymes catalyzing the formation of organosulfur natural products.

Theoretical Study of the Mechanism of the Nonheme Iron Enzyme EgtB

EgtB is a nonheme iron enzyme catalyzing the C-S bond formation between γ-glutamyl cysteine (γGC) and N-α-trimethyl histidine (TMH) in the ergothioneine biosynthesis. Density functional calculations were performed to elucidate and delineate the reaction mechanism of this enzyme. Two different mechanisms were considered, depending on whether the sulfoxidation or the S-C bond formation takes place first. The calculations suggest that the S-O bond formation occurs first between the thiolate and the ferric superoxide, followed by homolytic O-O bond cleavage, very similar to the case of cysteine dioxygenase. Subsequently, proton transfer from a second-shell residue Tyr377 to the newly generated iron-oxo moiety takes place, which is followed by proton transfer from the TMH imidazole to Tyr377, facilitated by two crystallographically observed water molecules. Next, the S-C bond is formed between γGC and TMH, followed by proton transfer from the imidazole CH moiety to Tyr377, which was calculated to be the rate-limiting step for the whole reaction, with a barrier of 17.9 kcal/mol in the quintet state. The calculated barrier for the rate-limiting step agrees quite well with experimental kinetic data. Finally, this proton is transferred back to the imidazole nitrogen to form the product. The alternative thiyl radical attack mechanism has a very high barrier, being 25.8 kcal/mol, ruling out this possibility.

Quality of Bread Supplemented with Antrodia salmonea-Fermented Grains

Fermented grains of buckwheat, oat, embryo rice and wheat, which were prepared by solid-state fermentation with Antrodia salmonea, and the mycelium was used to substitute 7% of wheat flour to make bread. No difference in proximate composition, texture profile and contents of non-volatile taste components was observed among bread samples. White bread and bread supplemented with mycelium and fermented grains looked different. Bread supplemented with fermented grains had similar thermal properties, which differed from those of white bread and bread supplemented with mycelium. Bread supplemented with fermented grains contained substantial mass fractions (on dry mass basis) of adenosine (0.92-1.96 µg/g), ergosterol (24.53-30.12 µg/g), ergothioneine (2.16-3.18 µg/g) and γ-aminobutyric acid (2.20-2.45 µg/g). In addition, bread supplemented with mycelium contained lovastatin (0.43 µg/g). White bread and bread supplemented with fermented grains had similar sensory results. Overall, fermented grains could be incorporated into bread to provide beneficial effects.

A Safety Evaluation of a Nature-Identical l-Ergothioneine in Sprague Dawley Rats

l-(+) Ergothioneine is a naturally occurring thiol amino acid with antioxidant properties and potential benefits as a dietary supplement. Despite its century-old identification and wide distribution in human food, little is known of its mechanism of action and safety. The nature-identical biomimetic of l-(+) ergothioneine, produced by Mironova Labs and supplied as Mironova (EGT+), has been investigated in the present studies for its mutagenic and toxicologic potential. In a plate incorporation and preincubation assay with Salmonella typhimurium strains TA98, 100, 1,535, and 1,537 and Escherichia coli WP2uvrA strain, at dose concentrations of 1.58, 5, 15.8, 50, 158, 500, 1,580, and 5,000 μg/plate with and without metabolic activation, no cytotoxicity or mutagenicity was observed. Following a preliminary 28-day study, a repeated dose 90-day gavage study at dose levels of 0, 400, 800, and 1,600 mg/kg body weight (bw)/d in Sprague Dawley rats, in which dose-proportional systemic absorption was confirmed by plasma analysis, no adverse clinical, body weight/gain, food consumption and efficiency, clinical pathology, or histopathological changes associated with the administration of the nature-identical ergothioneine were observed. In conclusion, EGT+ administered over 90 days was well tolerated with a no adverse effect level at 1,600 mg/kg bw/d, the highest dose tested for male and female rats. In addition, the nature-identical test substance, EGT+ was not mutagenic in a bacterial reverse mutation assay at plate concentrations of up to 5,000 μg/mL in the presence or absence of metabolic activation.