A new and versatile method for determination of thiolamines of biological importance

Quantitative analysis of electroporation-mediated intracellular delivery via bioorthogonal luminescent reaction

Efficient intracellular delivery is crucial for biotherapeutics, such as proteins, oligonucleotides, and CRISPR/Cas9 gene-editing systems, to achieve their efficacy. Despite the great efforts of developing new intracellular delivery carriers, the lack of straightforward methods for intracellular delivery quantification limits further development in this area. Herein, we designed a simple and versatile bioorthogonal luminescent reaction (BioLure assay) to analyze intracellular delivery. Our results suggest that BioLure can be used to estimate the amount of intracellularly delivered molecules after electroporation, and the estimation by BioLure is in good correlation with the results from complementary methods. Furthermore, we used BioLure assay to correlate the intracellularly-delivered RNase A amount with its tumoricidal activity. Overall, BioLure is a versatile tool for understanding the intracellular delivery process on live cells, and establishing the link between the cytosolic concentration of intracellularly-delivered biotherapeutics and their therapeutic efficacy.

Dimethyl Sulfoxide (DMSO) as a Potential Source of Interference in Research Related to Sulfur Metabolism-A Preliminary Study

Dimethyl sulfoxide (DMSO), an organosulfur compound, is widely used as the gold standard solvent in biological research. It is used in cell culture experiments and as a component of formulations in in vivo studies. Unfortunately, parameters related to sulfur metabolism are often not taken into account when using DMSO. Therefore, in this work we aim to show that the addition of DMSO to the culture medium (even in amounts commonly considered acceptable) alters some parameters of sulfur metabolism. For this study, we used three cell lines: a commercially available Caco-2 line (HTB-37, ATCC) and two lines created as part of our early studies (likewise previously described in the literature) to investigate the anomalies of sulfur metabolism in mucopolysaccharidosis. As the negative effects of DMSO on the cell membrane are well known, additional experiments with the partial loading of DMSO into polymerosomes (poly(ethylene glycol) methyl ether-block-poly(lactide-co-glycolide), PEG-PLGA) were performed to eliminate these potentially disruptive effects. The results show that DMSO is a source of interference in studies related to sulfur metabolism and that there are not just simple effects that can be corrected in the final result by subtracting control values, since complex synergisms are also observed.

Differences in nonoxidative sulfur metabolism between normal human breast MCF-12A and adenocarcinoma MCF-7 cell lines

Recent studies have revealed the role of endogenous hydrogen sulfide (H2S) in the development of breast cancer. The capacity of cells to generate H2S and the activity and expression of the main enzymes (cystathionine beta synthase; CBS, cystathionase γ-lyase; CGL, 3-mercaptopyruvate sulfurtransferase; MPST and thiosulfate sulfurtransferase; TST) involved in H2S metabolism were analyzed using an in vitro model of a non-tumourigenic breast cell line (MCF-12A) and a human breast adenocarcinoma cell line (MCF-7). In both cell lines, MPST, CGL, and TST expression was confirmed at the mRNA (RT-PCR) and the protein (Western Blot) level, while CBS expression was detected only in MCF-7 cells. Elevated levels of GSH, sulfane sulfur and increased CBS and TST activity were presented in the MCF-7 compared to the MCF-12A cells. It appears that cysteine might be mainly a substrate for GSH synthesis in breast adenocarcinoma. Increased capacity of the cells to generate H2S was shown for MCF-12A compared to MCF-7 cell line. Results suggest an important function of CBS in H2S metabolism in breast adenocarcinoma. The presented work may contribute to further research on new therapeutic possibilities for breast cancer - one of the most frequently diagnosed types of cancer among women.

Heart and kidney H2S production is reduced in hypertensive and older rats

The prevalence of hypertension increases with age, but the mechanisms linking this phenomenon are not well understood. Hydrogen sulfide (H₂S) may be involved in this process, as it plays a role in the cardiovascular system, affecting blood pressure and heart and kidney functions. The aim of this study was to evaluate the influence of hypertension and aging on sulfur-containing compounds metabolism in the hearts and kidneys of Wistar Kyoto (WKY) and Spontaneously Hypertensive Rats (SHR) of different age groups. We determined the expression and activity of four enzymes participating in H₂S production: cystathionine beta-synthase (CBS), cystathionine gamma-lyase (CTH), 3-mercaptopyruvate sulfurtransferase (MPST), and thiosulfate sulfurtransferase (TST). The levels of reduced/oxidized glutathione, cysteine, cystine, and cystathionine, and the ability of tissues to form hydrogen sulfide were also investigated. Tissues obtained from younger WKY rats produced the highest amounts of H₂S. The effect of hypertension on the metabolism of sulfur-containing compounds was manifested by a decrease in sulfane sulfur concentrations in heart homogenates and a decrease in CTH activity in the kidneys. The hearts and kidneys of older WKY rats were characterized by lower MPST or CTH gene expression, respectively, compared to younger animals. Our study demonstrates that hypertension and aging influence cardiac and renal sulfur-containing compounds metabolism and reduce H₂S production. Furthermore, we showed that MPST plays a major role in the production of hydrogen sulfide in the heart and CTH in the kidneys of rats.

The Cytotoxicity of OptiBond Solo Plus and Its Effect on Sulfur Enzymes Expression in Human Fibroblast Cell Line Hs27

The aim of the study was to determine the cytotoxic concentrations and incubation times of the commonly used dental adhesive system OptiBond Solo Plus in its non-polymerized form, and to test how it relates to oxidative stress by determining the reduced and oxidized glutathione (GSH and GSSG) levels as well as to study its influence on cell number and the expression of selected sulfur enzymes, with particular emphasis on cystathionine γ-lyase (CTH) and 3-mercaptopyruvate (MPST), sulfurtransferase. All investigations were conducted on an in vitro model of human fibroblast cell line Hs27. Changes in cellular plasma membrane integrity were measured by the LDH test. The expression levels were determined by RT-PCR and Western blot protocols. Changes in cell number were visualized using crystal violet staining. The RP-HPLC method was used to determine the GSH and GSSG levels. Reduced cell number was shown for all tested concentrations and times. Changes in the expression on the mRNA and protein level were demonstrated for CTH and MPST enzymes upon exposure to the tested range of OptiBond concentrations. Levels of low-molecular sulfur compounds of reduced and oxidized glutathione were also established. Cytotoxic effect of OptiBond Solo Plus may be connected with the changes of MPST and CTH sulfur enzymes in the human fibroblast Hs27 cell line. The elevated levels of these enzymes could possibly show the antioxidant response to this dental adhesive system. OptiBond Solo Plus in vitro results should be taken into consideration for further in vivo tests.

The Expression and Activity of Rhodanese, 3-Mercaptopyruvate Sulfurtransferase, Cystathionine γ-Lyase in the Most Frequently Chosen Cellular Research Models

This paper provides information concerning the activity and expression levels of three sulfurtransferases (STRs): rhodanese (TST, EC: 2.8.1.1), 3-mercaptopyruvate sulfurtransferase (MPST, EC: 2.8.1.2) and cystathionine γ-lyase (CTH, EC: 4.4.1.1) in various cell lines. Since very limited data are available in the scientific literature on this subject, the available data are included in this paper. These shortages often force the researchers to carry out their own screening tests that allow them to choose an appropriate model for their further studies. This work supplements the existing deficiencies in this area and presents the activity and expression of STRs in the eight most frequently chosen cell lines: the mouse mammary gland cell line (NMuNG, ATCC: CRL-1636), mouse mammary gland tumor (4T1, ATCC: CRL-2539), mouse fibroblast (MEF, ATCC: SCRC-1008), mouse melanoma (B16-F1, ATCC: CRL-6323), human colorectal adenocarcinoma (Caco-2, ATCC: HTB-37), human embryonic kidney (HEK-293, ATCC: CRL-1573), human osteosarcoma (MG-63, ATCC: CRL-1427) and rat myocardium (H9c2, ATCC: CRL-1446). Changes in STRs activity are directly related to the bioavailability of cysteine and the sulfane sulfur level, and thus the present authors also measured these parameters, as well as the level of glutathione (its reduced (GSH) and oxidized (GSSG) form) and the [GSH]/[GSSG] ratio that determines the antioxidant capacity of the cells. STRs demonstrate diverse functionality and clinical relevance; therefore, we also performed an analysis of genetic variation of STRs genes that revealed a large number of polymorphisms. Although STRs still provide challenges in several fields, responding to them could not only improve the understanding of various diseases, but may also provide a way to treat them.

Hyaluronic Acid-Based Nanocapsules as Efficient Delivery Systems of Garlic Oil Active Components with Anticancer Activity

Diallyl disulfide (DADS) and diallyl trisulfide (DATS) are garlic oil compounds exhibiting beneficial healthy properties including anticancer action. However, these compounds are sparingly water-soluble with a limited stability that may imply damage to blood vessels or cells after administration. Thus, their encapsulation in the oil-core nanocapsules based on a derivative of hyaluronic acid was investigated here as a way of protecting against oxidation and undesired interactions with blood and digestive track components. The nuclear magnetic resonance (¹H NMR) technique was used to follow the oxidation processes. It was proved that the shell of the capsule acts as a barrier limiting the sulfur oxidation, enhancing the stability of C=C bonds in DADS and DATS. Moreover, it was shown that the encapsulation inhibited the lysis of the red blood cell membrane (mainly for DADS) and interactions with serum or digestive track components. Importantly, the biological functions and anticancer activity of DADS and DATS were preserved after encapsulation. Additionally, the nanocapsule formulations affected the migration of neoplastic cells—a desirable preliminary observation concerning the inhibition of migration. The proposed route of administration of these garlic extract components would enable reaching their higher concentrations in blood, longer circulation in a bloodstream, and thus, imply a better therapeutic effect.

Hypertension and Aging Affect Liver Sulfur Metabolism in Rats

Hypertension and age are key risk factors for cardiovascular morbidity and mortality. Hydrogen sulfide (H2S), a gaseous transmitter, contributes significantly to regulating arterial blood pressure and aging processes. This study evaluated the effects of hypertension and aging on the hepatic metabolism of sulfur-containing compounds, the activity of the enzymes involved in sulfur homeostasis, and the liver's ability to generate H2S. Livers isolated from 16- and 60-week-old normotensive Wistar Kyoto rats (WKY) and Spontaneously Hypertensive Rats (SHR) were used to evaluate gene expression using RT-PCR, and the activity of enzymes participating in H2S metabolism, including thiosulfate sulfurtransferase (rhodanese; TST), cystathionine gamma-lyase (CTH), and 3-mercaptopyruvate sulfurtransferase (MPST). The levels of cysteine, cystine, reduced and oxidized glutathione were measured using RP-HPLC. SHR livers from both age groups showed a higher capacity to generate H2S than livers from WKY. The gene expression and activity of enzymes involved in sulfur metabolism differed between WKY and SHR, and between the age groups. For example, 16-week-old SHR had significantly higher activity of TST than 16-week-old WKY. Furthermore, differences between younger and older WKY rats in the expression and/or activity of TST and MPST were present. In conclusion, our study shows that arterial hypertension and aging affect hepatic sulfur metabolism and H2S production in rats. These findings pave the way for interventional studies evaluating a potential causal relation between liver sulfur metabolism, hypertension and aging.

Multidirectional Changes in Parameters related to Sulfur Metabolism in Frog Tissues exposed to Heavy Metal-related Stress

The investigations showed changes of the cystathionine γ-lyase (CTH), 3-mercaptopyruvate sulfurtransferase (MPST) and rhodanese (TST) activity and gene expression in the brain, heart, liver, kidney, skeletal muscles and testes in frogs Pelophylax ridibundus, Xenopus laevis and Xenopus tropicalis in response to Pb²⁺, Hg²⁺ and Cd²⁺ stress. The results were analyzed jointly with changes in the expression of selected antioxidant enzymes (cytoplasmic and mitochondrial superoxide dismutase, glutathione peroxidase, catalase and thioredoxin reducatase) and with the level of malondialdehyde (a product of lipid peroxidation). The obtained results allowed for confirming the role of sulfurtransferases in the antioxidant protection of tissues exposed to heavy metal ions. Our results revealed different transcriptional responses of the investigated tissues to each of the examined heavy metals. The CTH, MPST and TST genes might be regarded as heavy metal stress-responsive. The CTH gene expression up-regulation was confirmed in the liver (Pb²⁺, Hg²⁺, Cd²⁺) and skeletal muscle (Hg²⁺), MPST in the brain (Pb²⁺, Hg²⁺), kidney (Pb²⁺, Cd²⁺), skeletal muscle (Pb²⁺, Hg²⁺,Cd²⁺) and TST in the brain (Pb²⁺) and kidney (Pb²⁺, Hg²⁺, Cd²⁺). Lead, mercury and cadmium toxicity was demonstrated to affect the glutathione (GSH) and cysteine levels, the concentration ratio of reduced to oxidized glutathione ([GSH]/[GSSG]) and the level of sulfane sulfur-containing compounds, which in case of enhanced reactive oxygen species generation can reveal their antioxidative properties. The present report is the first to widely describe the role of the sulfane sulfur/H₂S generating enzymes and the cysteine/glutathione system in Pb²⁺, Hg²⁺ and Cd²⁺ stress in various frog tissues, and to explore the mechanisms mediating heavy metal-related stress.

A possible mechanism of inhibition of U87MG and SH-SY5Y cancer cell proliferation by diallyl trisulfide and other aspects of its activity

The study was conducted to elucidate the mechanism of antiproliferative and antioxidative action of diallyl trisulfide (DATS), a garlic-derived organosulfur compound. Changes in the l-cysteine desulfuration, and the levels of cystathionine and non-protein thiols in DATS-treated human glioblastoma (U87MG) and neuroblastoma (SH-SY5Y) cells were investigated. The inhibition of proliferation of the investigated cells by DATS was correlated with an increase in the inactivated form of Bcl-2. In U87MG cells, an increased level of sulfane sulfur and an increased activity of 3-mercaptopyruvate sulfurtransferase (MPST) and rhodanese, the enzymes involved in sulfane sulfur generation and transfer, suggest that DATS can function as a donor of sulfane sulfur atom, transferred by sulfurtransferases, to sulfhydryl groups of cysteine residues of Bcl-2 and in this way lower the level of active form of Bcl-2 by S-sulfuration. Diallyl trisulfide antioxidative effects result from an increased level of cystathionine, a precursor of cysteine, and an increased glutathione level. MPST and rhodanese, the level of which is increased in the presence of DATS, can serve as antioxidant proteins.

Hydrogen Sulphide Production in Healthy and Ulcerated Gastric Mucosa of Rats

Hydrogen sulphide (H₂S) is produced endogenously via two enzymes dependent on pyridoxal phosphate (PLP): cystathionine beta-synthase (CBS, EC 4.2.1.22), cystathionase γ-liase (CTH, EC 4.4.1.1), and a third, 3-mercaptopyruvate sulfurtransferase (MPST, EC 2.8.1.2). H₂S strengthens the defence mechanisms of the gastric mucosal barrier, and plays an important role in gastroprotection, including the increased resistance to damage caused by various irritants and non-steroidal anti-inflammatory drugs. The study was conducted to determine the role of H₂S in ulcerated gastric mucosa of rats caused by immobilization in cold water (WRS). The activity and expression of γ-cystathionase, cystathionine β-synthase, 3-mercaptopyruvate sulfurtransferase, and rhodanese was compared with healthy mucosa, together with H₂S generation, and cysteine, glutathione, and cystathionine levels. The results showed that the defence mechanism against stress is associated with stimulation of the production of H₂S in the tissue and confirmed the observed advantageous effect of H₂S on healing of gastric ulcers. In case of animals pretreated with exogenous sources of H₂S and NaHS, and some changes observed in the ulcerated gastric mucosa tend to return to values found in the healthy tissue, a finding that is in accordance with the previously determined gastroprotective properties of H₂S. The results presented in this paper point to the possible role of rhodanese in H₂S production in the gastric mucosa of rats, together with the earlier mentioned three enzymes, which are all active in this tissue.

Is development of high-grade gliomas sulfur-dependent?

We characterized γ-cystathionase, rhodanese and 3-mercaptopyruvate sulfurtransferase activities in various regions of human brain (the cortex, thalamus, hypothalamus, hippocampus, cerebellum and subcortical nuclei) and human gliomas with II to IV grade of malignancy (according to the WHO classification). The human brain regions, as compared to human liver, showed low γ-cystathionase activity. The activity of rhodanese was also much lower and it did not vary significantly between the investigated brain regions. The activity of 3-mercaptopyruvate sulfurtransferase was the highest in the thalamus, hypothalamus and subcortical nuclei and essentially the same level of sulfane sulfur was found in all the investigated brain regions. The investigations demonstrated that the level of sulfane sulfur in gliomas with the highest grades was high in comparison to various human brain regions, and was correlated with a decreased activity of γ-cystathionase, 3-mercaptopyruvate sulfurtransferase and rhodanese. This can suggest sulfane sulfur accumulation and points to its importance for malignant cell proliferation and tumor growth. In gliomas with the highest grades of malignancy, despite decreased levels of total free cysteine and total free glutathione, a high ratio of GSH/GSSG was maintained, which is important for the process of malignant cells proliferation. A high level of sulfane sulfur and high GSH/GSSG ratio could result in the elevated hydrogen sulfide levels. Because of the disappearance of γ-cystathionase activity in high-grade gliomas, it seems to be possible that 3-mercaptopyruvate sulfurtransferase could participate in hydrogen sulfide production. The results confirm sulfur dependence of malignant brain tumors.

An application of RP-HPLC for determination of the activity of cystathionine β-synthase and γ-cystathionase in tissue homogenates

The RP-HPLC-based method of determination of the activity of cystathionine β-synthase and γ-cystathionase was undertaken in mouse liver, kidney and brain. Products of the reactions, such as cystathionine, α-ketobutyrate, cysteine and glutathione, were measured using the RP-HPLC method. A difference in the cystathionine level between homogenates with totally CTH-inhibiting concentrations of DL-propargylglycine and without the inhibitor was employed to evaluate the activity of cystathionine β-synthase. Gamma-cystathionase activity was measured using DL-homoserine as a substrate and a sensitive HPLC-based assay to measure α-ketobutyrate. The results confirmed high cystathionine β-synthase activity and no γ-cystathionase activity in brain, and high γ-cystathionase activity in mouse liver. The method presented here allows for evaluating the relative contribution of CBS and CTH to generation of H2S in tissues. Additionally, it provides results, which reflect the redox status (GSH/GSSG) of a tissue.

Exposure to lead in water and cysteine non-oxidative metabolism in Pelophylax ridibundus tissues

Chronic, low-level exposure to metals is an increasing global problem. Lead is an environmentally persistent toxin that causes many lead-related pathologies, directly affects tissues and cellular components or exerts an effect of the generation of reactive oxygen species causing a diminished level of available sulfhydryl antioxidant reserves. Cysteine is one of substrates in the synthesis of glutathione - the most important cellular antioxidant, and it may also undergo non-oxidative desulfuration that produces compounds containing sulfane sulfur atoms. The aim of the experiment was to examine changes of the non-oxidative metabolism of cysteine and the levels of cysteine and glutathione in the kidneys, heart, brain, liver and muscle of Marsh frogs (Pelophylax ridibundus) exposed to 28mg/L Pb(NO(3))(2) for 10 days. The activities of sulfurtransferases, enzymes related to the sulfane sulfur metabolism - 3-mercaptopyruvate sulfurtransfearse, γ-cystathionase and rhodanese - were detected in tissue homogenates. The activity of sulfurtransferases was much higher in the kidneys of frogs exposed to lead in comparison to control frogs, not exposed to lead. The level of sulfane sulfur remained unchanged. Similarly, the total level of cysteine did not change significantly. The total levels of glutathione and the cysteine/cystine and GSH/GSSG ratios were elevated. Thus, it seems that the exposure to lead intensified the metabolism of sulfane sulfur and glutathione synthesis in the kidneys. The results presented in this work not only confirm the participation of GSH in the detoxification of lead ions and/or products appearing in response to their presence, such as reactive oxygen species, but also indicate the involvement of sulfane sulfur and rhodanese in this process (e.g. brain). As long as the expression of enzymatic proteins (rhodanese, MPST and CST) is not examined, no answer will be provided to the question whether changes in their activity are due to differences in the concentrations of substrates and/or compounds affecting their activity or to changes in their level in response to some parameters, e.g. associated with oxidative stress.

Upregulation of chemoprotective enzymes and glutathione by Nigella sativa (black seed) and thymoquinone in CCl4-intoxicated rats

To examine the hepatoprotective activities of Nigella sativa (Ns) and thymoquinone (TQ) against carbon tetrachloride (CCl(4))-induced hepatotoxicity, the effects of water extract of Ns seeds (50 mg/kg) or TQ (5 mg/kg in corn oil) by gavage for 5 days on detoxifying enzymes and glutathione were compared in healthy and CCl(4)-challenged (1 mL/kg in corn oil, intraperitoneally [ip], a single dose) rats. Both Ns and TQ countered the elevations in serum alanine aminotransferase activity, oxidized glutathione level, and stress ratio caused by CCl(4). Both Ns and TQ ameliorated the reductions in the activities and messenger RNA (mRNA) levels of glutathione S-transferase, NAD(P)H-quinone oxidoreductase, and microsomal epoxide hydrolase, as well as the reductions in reduced glutathione and cysteine levels produced by CCl(4). In many instances, Ns was much superior to TQ in providing protection against the damaging effects caused by CCl(4). This protection could be attributed to the induction of chemoprotective enzymes probably through increasing transcription.

Effect of mercury ions on cysteine metabolism in Xenopus laevis tissues

The effect of mercury ions on the level of cysteine, glutathione, sulfane sulfur, and on the activity of rhodanese, 3-mercaptopyruvate sulfurtransferase (MPST) and γ-cystathionase in brain, heart muscle, liver, kidneys, testes and skeletal muscle of adult Xenopus laevis was investigated. Frogs of both sexes were exposed for 7 or 14 days to 1.353mgL(-1) (ppm) of mercury chloride (HgCl(2)) dissolved in water. The activity of the investigated enzymes participating in cysteine metabolism depends on cysteine in their active sites. Mercury ions can bind to -SH groups and, therefore, lower the activity of enzymes and change the level of sulfane sulfur, a product of l-cysteine desulfuration. The effect of mercury was found to depend on the time of exposure and the kind of tissue. In the liver, the main site of glutathione biosynthesis, the ratio of GSH to GSSG was essentially unchanged. The total glutathione level was decreased after 7 days of exposure to mercury, similarly as the activity of rhodanese. Sulfane sulfur levels were significantly increased after a shorter duration, while they decreased after a longer time of exposure. The kidney, brain and testes were able to enhance the level of GSH, probably thanks to high γ-glutamyltranspeptidase activity. These tissues showed an increased value of GSH/GSSG ratio during the shorter exposure to mercury. The activity of sulfurtransferases was decreased, especially after the longer exposure to mercury. In the heart and skeletal muscle, the level of GSH, sulfane sulfur, and the activity of the investigated sulfurtransferases was diminished after 14 days of exposure to Hg. It can be concluded that the main mechanism of toxic Hg activity is generation of reactive oxygen species in cells due to depleted GSH level, and a decreased sulfurtransferases activity either by blocking or oxidation of their -SH groups, what in consequence results in a diminished sulfane sulfur levels in tissues, especially the heart and testes.

The expression and activity of cystathionine-γ-lyase and 3-mercaptopyruvate sulfurtransferase in human neoplastic cell lines

The expression and activity of cystathionine γ-lyase (CST) and 3-mercaptopyruvate sulfurtransferase (MPST) were investigated in the human neoplastic cells lines: astrocytoma U373, neuroblastoma SH-SY5Y, melanoma A375, and melanoma WM35. Gene expression analysis demonstrated that the investigated neoplastic cells showed the expression of MPST and what is particularly interesting, the expression of CST. The presence of CST in these cells was confirmed using RT-PCR and western blot analysis. However, in U373 cells, a very low activity of CST was detected. In all the investigated cell lines, the activity of MPST was higher than that of CST, which suggests that in these cells, the main pathway of sulfane sulfur formation is the MPST-catalyzed reaction. RP-HPLC analysis showed a large disparity between the level of cystathionine and GSH in the investigated neoplastic cells. In SH-SY5Y cells, the low level of GSH and low GSH/GSSG ratio corresponded with the highest CST activity. Further investigations could aim at verifying whether the stimulation of CST, at the level of protein or gene expression, could change the proliferation of neoplastic cells.

Age-related changes in antioxidant enzymes related to hydrogen peroxide metabolism in rat inner ear

Oxidative stress is a pervasive factor in aging and has been implicated in noise-induced cochlear pathology. In this study, we measured the activities of two enzymes that catalyze the removal of hydrogen peroxide (H(2)O(2)), catalase and glutathione peroxidase (Gpx), in 3- and 24-month-old Fisher-344 rats, and reduced and oxidized glutathione in 3-, 12-, and 24-month-old rats. There was an increase in Gpx activity in vascular tissue (spiral ligament and stria vascularis), but no change in modiolar, sensory or vestibular tissue of the cochlea. The elevation in vascular tissue was age-related. We observed a significant elevation of catalase activity in vestibular tissue, a tendency for age-related elevation in the modiolus, but no change in vascular or sensory cochlear tissue. These findings suggest that increased Gpx activity in vascular cochlear tissue may be an age-related compensation for a decrease in glutathione and a decline in the redox state measured by the ratio of reduced to oxidized glutathione.

The level of sulfane sulfur in the fungus Aspergillus nidulans wild type and mutant strains

The interdependence of the sulfane sulfur metabolism and sulfur amino acid metabolism was studied in the fungus Aspergillus nidulans wild type strain and in mutants impaired in genes encoding enzymes involved in the synthesis of cysteine (a precursor of sulfane sulfur) or in regulatory genes of the sulfur metabolite repression system. It was found that a low concentration of cellular cysteine leads to elevation of two sulfane sulfurtransferases, rhodanase and cystathionine gamma-lyase, while the level of 3-mercaptopyruvate sulfurtransferase remains largely unaffected. In spite of drastic differences in the levels of biosynthetic enzymes and of sulfur amino acids due to mutations or sulfur supplementation of cultures, the level of total sulfane sulfur is fairly stable. This stability confirms the crucial role of sulfane sulfur as a fine-tuning regulator of cellular metabolism.

N-acetylcysteine protects melanocytes against oxidative stress/damage and delays onset of ultraviolet-induced melanoma in mice

PURPOSE

UV radiation is the major environmental risk factor for melanoma and a potent inducer of oxidative stress, which is implicated in the pathogenesis of several malignancies. We evaluated whether the thiol antioxidant N-acetylcysteine (NAC) could protect melanocytes from UV-induced oxidative stress/damage in vitro and from UV-induced melanoma in vivo.

EXPERIMENTAL DESIGN

In vitro experiments used the mouse melanocyte line melan-a. For in vivo experiments, mice transgenic for hepatocyte growth factor and survivin, shown previously to develop melanoma following a single neonatal dose of UV irradiation, were given NAC (7 mg/mL; mother's drinking water) transplacentally and through nursing until 2 weeks after birth.

RESULTS

NAC (1-10 mmol/L) protected melan-a cells from several UV-induced oxidative sequelae, including production of intracellular peroxide, formation of the signature oxidative DNA lesion 8-oxoguanine, and depletion of free reduced thiols (primarily glutathione). Delivery of NAC reduced thiol depletion and blocked formation of 8-oxoguanine in mouse skin following neonatal UV treatment. Mean onset of UV-induced melanocytic tumors was significantly delayed in NAC-treated compared with control mice (21 versus 14 weeks; P = 0.0003).

CONCLUSIONS

Our data highlight the potential importance of oxidative stress in the pathogenesis of melanoma and suggest that NAC may be useful as a chemopreventive agent.

Low Part per Trillion Determination of Reactive Alkanethiols in Wastewater by in Situ Derivatization-Solid-Phase Microextraction Followed by GC/MS

A solid-phase microextraction (SPME) procedure for the simultaneous determination of volatile alkanethiols (i.e., methane-, ethane-, propanethiol) and dihydrogen sulfide in aqueous samples as stable thioethers followed by GC/MS determination was developed. Accordingly, N-ethylmaleimide as derivatization reagent in the aqueous phase was used for the first time, improving the analyte stability and method sensitivity in comparison to the determination of free forms. Thus, pH of the aqueous medium, reaction time, and derivatization reagent concentration have been evaluated, and the main parameters affecting the SPME process (i.e., coating selection, extraction mode and time profile, extraction and desorption temperatures) optimized. At the selected derivatization and extraction conditions, the proposed method provided no matrix effect either in the derivatization reaction or in the microextraction steps. RSD values were lower than 11% and LODs from 0.74 to 5.2 ng L(-1). The developed procedure was successfully applied to different water and wastewater samples, where dihydrogen sulfide and some of the target alkanethiols were identified at low-microgram per liter concentrations.

Quantitative Measurements of Oxidative Stress in Mouse Skin Induced by X-Ray Irradiation

To find efficient methods to evaluate oxidative stress in mouse skin caused by X-ray irradiation, several markers and methodologies were examined. Hairless mice were irradiated with 50 Gy X-rays and skin homogenates or skin strips were prepared. Lipid peroxidation was measured using the skin homogenate as the level of thiobarbituric acid reactive substances. The level of lipid peroxidation increased with time after irradiation and was twice that of the control at 78 h. ESR spectra of skin strips showed a clear signal for the ascorbyl radical, which increased with time after irradiation in a manner similar to that of lipid peroxidation. To measure levels of glutathione (GSH) and its oxidized forms (GSSG) simultaneously, two HPLC methods, sample derivatization with 1-fluoro-2,4-dinitrobenzene and detection with a UV detector (method A) and no derivatization and detection with an electrochemical detector (method B), were compared and the latter was found to be better. No significant change was observed within 24 h after irradiation in the levels of GSH and GSSG measured by method B. The GSH/GSSG ratio may be a less sensitive parameter for the evaluation of acute oxidative stress caused by X-ray irradiation in the skin. Monitoring the ascorbyl radical seems to be a good way to evaluate oxidative stress in skin in vivo.

Analytical methods to investigate glutathione and related compounds in biological and pathological processes

Reduced glutathione (GSH, gamma-L-glutamyl-L-cysteinylglycine) is a fundamental low-molecular mass antioxidant that serves several biological functions. Upon enzymatic and non-enzymatic oxidation, GSH forms glutathione disulfide (GSSG) and, under particular conditions, may generate other oxidative products. The determination of GSH, its precursors, and metabolites in several bio-matrices is a useful tool in studying oxidative stress. Many separative and non-separative methods have been developed and improved for the assay of GSH and related compounds. At present, high-performance liquid chromatography and capillary electrophoresis are the most used separative techniques to determine GSH and congeners. The review will deal with analytical methods developed over the last few years for the determination of GSH and related compounds, and with the procedures performed in sample pre-treatment in order to minimize analytical errors. Since GSH, GSSG, and related compounds lack of strong chromophores or fluorophores, it is advantageous, in many assays, to derivatize the compounds in order to improve the detection limit with UV-Vis and to allow fluorescence, thus the most commonly used labeling agents are also described.