Skin cells and tissue are capable of using L-ergothioneine as an integral component of their antioxidant defense system

Hydrogen sulfide donors in research and drug development

This review summarized most of the H₂S donors such as inorganic compounds, natural products, anethole trithione derivatives and synthetic compounds used in research and drug development. These special bioactivities provided us some effective strategies for antiphlogosis, cancer therapy, cardiovascular protection and so on.

Phytoagents for cancer management: regulation of nucleic acid oxidation, ROS, and related mechanisms

Accumulation of oxidized nucleic acids causes genomic instability leading to senescence, apoptosis, and tumorigenesis. Phytoagents are known to reduce the risk of cancer development; whether such effects are through regulating the extent of nucleic acid oxidation remains unclear. Here, we outlined the role of reactive oxygen species in nucleic acid oxidation as a driving force in cancer progression. The consequential relationship between genome instability and cancer progression highlights the importance of modulation of cellular redox level in cancer management. Current epidemiological and experimental evidence demonstrate the effects and modes of action of phytoagents in nucleic acid oxidation and provide rationales for the use of phytoagents as chemopreventive or therapeutic agents. Vitamins and various phytoagents antagonize carcinogen-triggered oxidative stress by scavenging free radicals and/or activating endogenous defence systems such as Nrf2-regulated antioxidant genes or pathways. Moreover, metal ion chelation by phytoagents helps to attenuate oxidative DNA damage caused by transition metal ions. Besides, the prooxidant effects of some phytoagents pose selective cytotoxicity on cancer cells and shed light on a new strategy of cancer therapy. The “double-edged sword” role of phytoagents as redox regulators in nucleic acid oxidation and their possible roles in cancer prevention or therapy are discussed in this review.

The SLC22 family with transporters of organic cations, anions and zwitterions

The SLC22 family contains 13 functionally characterized human plasma membrane proteins each with 12 predicted α-helical transmembrane domains. The family comprises organic cation transporters (OCTs), organic zwitterion/cation transporters (OCTNs), and organic anion transporters (OATs). The transporters operate as (1) uniporters which mediate facilitated diffusion (OCTs, OCTNs), (2) anion exchangers (OATs), and (3) Na(+)/zwitterion cotransporters (OCTNs). They participate in small intestinal absorption and hepatic and renal excretion of drugs, xenobiotics and endogenous compounds and perform homeostatic functions in brain and heart. Important endogeneous substrates include monoamine neurotransmitters, l-carnitine, α-ketoglutarate, cAMP, cGMP, prostaglandins, and urate. It has been shown that mutations of the SLC22 genes encoding these transporters cause specific diseases like primary systemic carnitine deficiency and idiopathic renal hypouricemia and are correlated with diseases such as Crohn's disease and gout. Drug-drug interactions at individual transporters may change pharmacokinetics and toxicities of drugs.

Ergothioneine is a secreted antioxidant in Mycobacterium smegmatis

Ergothioneine (ERG) and mycothiol (MSH) are two low-molecular-weight thiols synthesized by mycobacteria. The role of MSH has been extensively investigated in mycobacteria; however, little is known about the role of ERG in mycobacterial physiology. In this study, quantification of ERG at various points in the growth cycle of Mycobacterium smegmatis revealed that a significant portion of ERG is found in the culture media, suggesting that it is actively secreted. A mutant of M. smegmatis lacking egtD (MSMEG_6247) was unable to synthesize ERG, confirming its role in ERG biosynthesis. Deletion of egtD from wild-type M. smegmatis and an MSH-deficient mutant did not affect their susceptibility to antibiotics tested in this study. The ERG- and MSH-deficient double mutant was significantly more sensitive to peroxide than either of the single mutants lacking either ERG or MSH, suggesting that both thiols play a role in protecting M. smegmatis against oxidative stress and that ERG is able to partly compensate for the loss of MSH.

Glutathione analogs in prokaryotes

BACKGROUND

Oxygen is both essential and toxic to all forms of aerobic life and the chemical versatility and reactivity of thiols play a key role in both aspects. Cysteine thiol groups have key catalytic functions in enzymes but are readily damaged by reactive oxygen species (ROS). Low-molecular-weight thiols provide protective buffers against the hazards of ROS toxicity. Glutathione is the small protective thiol in nearly all eukaryotes but in prokaryotes the situation is far more complex.

SCOPE OF REVIEW

This review provides an introduction to the diversity of low-molecular-weight thiol protective systems in bacteria. The topics covered include the limitations of cysteine as a protector, the multiple origins and distribution of glutathione biosynthesis, mycothiol biosynthesis and function in Actinobacteria, recent discoveries involving bacillithiol found in Firmicutes, new insights on the biosynthesis and distribution of ergothioneine, and the potential protective roles played by coenzyme A and other thiols.

MAJOR CONCLUSIONS

Bacteria have evolved a diverse collection of low-molecular-weight protective thiols to deal with oxygen toxicity and environmental challenges. Our understanding of how many of these thiols are produced and utilized is still at an early stage.

GENERAL SIGNIFICANCE

Extensive diversity existed among prokaryotes prior to evolution of the cyanobacteria and the development of an oxidizing atmosphere. Bacteria that managed to adapt to life under oxygen evolved, or acquired, the ability to produce a variety of small thiols for protection against the hazards of aerobic metabolism. Many pathogenic prokaryotes depend upon novel thiol protection systems that may provide targets for new antibacterial agents. This article is part of a Special Issue entitled Cellular functions of glutathione.

Differential response of normal human epidermal keratinocytes and HaCaT cells to hydrogen peroxide-induced oxidative stress

BACKGROUND

  Normal human epidermal keratinocytes (NHEKs) and HaCaT cells are the most common models used to study the effects of various factors on skin cells. These cell lines share some common characteristics, but little is known about their differences in handling hydrogen peroxide (H(2) O(2) )-induced oxidative stress.

AIM

To investigate the differential response of NHEKs and HaCaT cells to H(2) O(2) -induced oxidative stress.

METHODS

We examined differences in NHEKs and HaCaT cells after H(2) O(2) treatment, assessing changes in cell viability; levels of intracellular reactive oxygen species (ROS), superoxide dismutase (SOD) and caspase-3/7; percentage of cells arrested in G1 phase; number of senescence-associated β-galactosidase (SA-β-Gal)-positive cells and; expression of senescence-related protein Klotho.

RESULTS

The viability of NHEKs and HaCaT cells decreased in a concentration-dependent and time-dependent manner after exposure to H(2) O(2) . The inhibitory effect of 150 μmol/L H(2) O(2) on cell viability was greater in HaCaT cells than in NHEKs (P<0.05). Levels of ROS and caspase-3/7, and the percentage of cells arrested in G1 phase, were higher in HaCaT cells than in NHEKs, whereas intracellular SOD was higher in NHEKs than in HaCaT cells after exposure to 150 μmol/L H(2) O(2) (P < 0.05). SA-β-Gal positive cells increased significantly in NHEKs after treatment with H(2) O(2) (P < 0.05). Klotho was significantly downregulated in both NHEKs and HaCaT cells after H(2) O(2) treatment, but no SA-β-Gal-positive HaCaT cells were seen, even after treatment with H(2) O(2) .

CONCLUSIONS

Normal human epidermal keratinocytes are more resistant than HaCaT cells to H(2) O(2) -induced oxidative stress. HaCaT cells have senescence phenotypes, but do not express β-Gal.

Ergothioneine; antioxidant potential, physiological function and role in disease

Since its discovery, the unique properties of the naturally occurring amino acid, L-ergothioneine (EGT; 2-mercaptohistidine trimethylbetaine), have intrigued researchers for more than a century. This widely distributed thione is only known to be synthesized by non-yeast fungi, mycobacteria and cyanobacteria but accumulates in higher organisms at up to millimolar levels via an organic cation transporter (OCTN1). The physiological role of EGT has yet to be established. Numerous in vitro assays have demonstrated the antioxidant and cytoprotective capabilities of EGT against a wide range of cellular stressors, but an antioxidant role has yet to be fully verified in vivo. Nevertheless the accumulation, tissue distribution and scavenging properties, all highlight the potential for EGT to function as a physiological antioxidant. This article reviews our current state of knowledge. This article is part of a Special Issue entitled: Antioxidants and Antioxidant Treatment in Disease.

Effectiveness of sulfur-containing antioxidants in delaying skeletal muscle fatigue

Reactions involving thiol biochemistry seem to play a crucial role in skeletal muscle fatigue. N-acetylcysteine amide (NACA) and L-ergothioneine (ERGO) are thiol-based antioxidants available for human use that have not been evaluated for effects on muscle fatigue.

PURPOSE

To test the hypothesis that NACA and ERGO delay skeletal muscle fatigue.

METHODS

We exposed mouse diaphragm fiber bundles to buffer (CTRL), NACA, ERGO, or N-acetylcysteine (NAC; positive control). Treatments were performed in vitro using 10 mM for 60 min at 37 °C. After treatment, we determined the muscle force-frequency and fatigue characteristics.

RESULTS

The force-frequency relationship was shifted to the left by ERGO and to the right by NACA compared with CTRL and NAC. Maximal tetanic force was similar among groups. The total force-time integral (FTI; N · s · cm) during the fatigue trial was decreased by NACA (420 ± 35, P < 0.05), unaffected by ERGO (657 ± 53), and increased by NAC (P < 0.05) compared with CTRL (581 ± 54). The rate of contraction (dF/dtMAX) during the fatigue trial was not affected by any of the treatments tested. NAC, but not NACA or ERGO, delayed the slowing of muscle relaxation (dF/dtMIN) during fatigue.

CONCLUSIONS

In summary, NACA and ERGO did not delay skeletal muscle fatigue in vitro. We conclude that these antioxidants are unlikely to improve human exercise performance.

Crohn's disease and genetic hitchhiking at IBD5

Inflammatory bowel disease 5 (IBD5) is a 250 kb haplotype on chromosome 5 that is associated with an increased risk of Crohn's disease in Europeans. The OCTN1 gene is centrally located on IBD5 and encodes a transporter of the antioxidant ergothioneine (ET). The 503F variant of OCTN1 is strongly associated with IBD5 and is a gain-of-function mutation that increases absorption of ET. Although 503F has been implicated as the variant potentially responsible for Crohn's disease susceptibility at IBD5, there is little evidence beyond statistical association to support its role in disease causation. We hypothesize that 503F is a recent adaptation in Europeans that swept to relatively high frequency and that disease association at IBD5 results not from 503F itself, but from one or more nearby hitchhiking variants, in the genes IRF1 or IL5. To test for evidence of recent positive selection on the 503F allele, we employed the iHS statistic, which was significant in the European CEU HapMap population (P=0.0007) and European Human Genome Diversity Panel populations (P≤0.01). To evaluate the hypothesis of disease-variant hitchhiking, we performed haplotype association tests on high-density microarray data in a sample of 1,868 Crohn's disease cases and 5,550 controls. We found that 503F haplotypes with recombination breakpoints between OCTN1 and IRF1 or IL5 were not associated with disease (odds ratio [OR]: 1.05, P=0.21). In contrast, we observed strong disease association for 503F haplotypes with no recombination between these three genes (OR: 1.24, P=2.6×10(-8)), as expected if the sweeping haplotype harbored one or more disease-causing mutations in IRF1 or IL5. To further evaluate these disease-gene candidates, we obtained expression data from lower gastrointestinal biopsies of healthy individuals and Crohn's disease patients. We observed a 72% increase in gene expression of IRF1 among Crohn's disease patients (P=0.0006) and no significant difference in expression of OCTN1. Collectively, these data indicate that the 503F variant has increased in frequency due to recent positive selection and that disease-causing variants in linkage disequilibrium with 503F have hitchhiked to relatively high frequency, thus forming the IBD5 risk haplotype. Finally, our association results and expression data support IRF1 as a strong candidate for Crohn's disease causation.

The Effect of Ergothioneine on Clastogenic Potential and Mutagenic Activity

L-(+)-ergothioneine has antioxidant and anti-inflammatory properties in vitro and in vivo and has uses as a dietary supplement and as an ingredient in foods, cosmetics, and as a pharmaceutical additive. The clastogenic potential and mutagenic of ergothioneine were assessed in vitro and in vivo. Ergothioneine concentrations up to 5000 μg/mL, with and without metabolic activation, was tested in the chromosome aberration assay with CHL cells and found not to induce structural chromosome aberrations. In the in vivo mammalian erythrocyte micronucleus test, ergothioneine was administered orally to male mice at doses up to 1500 mg/kg for potential genotoxic activity. No increase in the frequency of micronucleated polychromatic erythrocytes was observed.  Overall, ergothioneine was not genotoxic in these studies and provides additional experimental evidence supporting the safety of its use as a potential dietary supplement.

Top 10 botanical ingredients in 2010 anti-aging creams

New developments in the realm of skin rejuvenation such as phytotherapy are at an astounding increasing pace in the cosmeceutical market. Yet, many of these products that are classified as cosmeceuticals are tested less vigorously and do not have to be approved by the Food and Drug Administration to establish efficacy and safety. Thus, as clinicians, we must ask the question, "Is there science-based evidence to validate the mechanism of these new treatments?" We assessed the top anti-aging creams currently on the market specifically evaluating their botanical ingredients. Some of the most common botanicals that are hot off the market are: Rosmarinus officinalis, Vitis vinifera (grape seed extract), Citronellol, Limonene, Oenothera biennis (evening primrose), Glycyrrhiza glabra (licorice extract), Aframomum angustifolium seed extract, Diosgenin (wild yam), N6 furfuryladenine (kinetin), and Ergothioneine. Through researching each of these botanical ingredients, we have concluded that randomized controlled trials are still needed in this area, but there is promise in some of these ingredients and science to validate them.

The unusual amino acid L-ergothioneine is a physiologic cytoprotectant

Ergothioneine (ET) is an unusual sulfur-containing derivative of the amino acid, histidine, which is derived exclusively through the diet. Although ET was isolated a century ago, its physiologic function has not been clearly established. Recently, a highly specific transporter for ET (ETT) was identified in mammalian tissues, which explains abundant tissue levels of ET and implies a physiologic role. Using RNA interference, we depleted cells of its transporter. Cells lacking ETT are more susceptible to oxidative stress, resulting in increased mitochondrial DNA damage, protein oxidation and lipid peroxidation. ETT is concentrated in mitochondria, suggesting a specific role in protecting mitochondrial components such as DNA from oxidative damage associated with mitochondrial generation of superoxide. In combating cytotoxic effects of pyrogallol, a known superoxide generator, ET is as potent as glutathione. Because of its dietary origin and the toxicity associated with its depletion, ET may represent a new vitamin whose physiologic roles include antioxidant cytoprotection.