Uniformly bounded Nemytskij operators acting between the Banach spaces of generalized Hölder functions

We investigate the Nemytskij (composition, superposition) operators acting between Banach spaces of r -times differentiable functions defined on the closed intervals of the real line with the r-derivatives satisfying a generalized Hölder condition. The main result says that if such a Nemytskij operator is uniformly bounded (in a special case uniformly continuous) then its generator is an affine function with respect to the second variable, i.e., the Matkowski representation holds. This extends an earlier result where an operator is assumed to be Lipschitzian

Atomic sulfur : an element for adaptation to an oxidative environment

During the period of rising oxygen concentration in the Earth’s atmosphere (Figure 1), sulfur atoms were incorporated into proteins as redox-active cysteine residues [1] and antioxidant molecules such as thioredoxin, glutathione, and glutaredoxin appeared [...

Menadione effect on l-cysteine desulfuration in U373 cells

The non-cytotoxic concentration (20 µM) of menadione (2-methyl-1,4-naphthoquinone), after 1 h of incubation, leads to loss of the activity of rhodanese by 33%, 3-mercaptopyruvate sulfurtransferase by 20%, as well as the level of sulfane sulfur by about 23% and glutathione by 12%, in the culture of U373 cells, in comparison with the control culture. Reactive oxygen species generated by menadione oxidize sulfhydryl groups in active centers of the investigated enzymes, inhibiting them and saving cysteine for glutathione synthesis. A decreased sulfane sulfur level can be correlated with an oxidative stress

Multidirectional changes in parameters related to sulfur metabolism in frog tissues exposed to heavy metal-related stress

The investigations showed changes of the cystathionine $\gamma$ -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 Pb$^{2+}$, Hg$^{2+}$ and Cd$^{2+}$ stress. The results were analyzed jointly w ith 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 w as confirmed in the liver (Pb$^{2+}$, Hg$^{2+}$, Cd$^{2+}$) and skeletal muscle (Hg$^{2+}$), MPST in the brain (Pb$^{2+}$ , Hg$^{2+}$), kidney (Pb$^{2+}$, Cd$^{2+}$ ), skeletal muscle (Pb$^{2+}$, Hg$^{2+}$,Cd$^{2+}$) and TST in the brain (Pb$^{2+}$) and kidney (Pb$^{2+}$, Hg$^{2+}$, Cd$^{2+}$ ). 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/H$_{2}$S generating enzymes and the cysteine/glutathione system in Pb$^{2+}$, Hg$^{2+}$ and Cd$^{2+}$ stress in various frog tissues, and to explore the mechanisms mediating heavy metal-related stress

Hydrogen sulfide generation from l-cysteine in the human glioblastoma-astrocytoma U-87 MG and neuroblastoma SHSY5Y cell lines

Hydrogen sulfide (H2S) is endogenously synthesized from l-cysteine in reactions catalyzed by cystathionine beta-synthase (CBS, EC 4.2.1.22) and gamma-cystathionase (CSE, EC 4.4.1.1). The role of 3-mercaptopyruvate sulfurtransferase (MPST, EC 2.8.1.2) in H2S generation is also considered; it could be important for tissues with low CTH activity, e.g. cells of the nervous system. The expression and activity of CBS, CTH, and MPST were detected in the human glioblastoma-astrocytoma (U-87 MG) and neuroblastoma (SHSY5Y) cell lines. In both cell lines, the expression and activity of MPST were the highest among the investigated enzymes, suggesting its possible role in the generation of H2S. The RP-HPLC method was used to determine the concentration of cystathionine and alpha-ketobutyrate, products of the CBS- and CTH-catalyzed reactions. The difference in cystathionine levels between cell homogenates treated with totally CTH-inhibiting concentrations of dl-propargylglycine and without the inhibitor was used to evaluate the activity of CBS. The higher expression and activity of CBS, CTH and MPST in the neuroblastoma cells were associated with more intensive generation of H2S in the presence of 2 mM cysteine. A threefold higher level of sulfane sulfur, a potential source of hydrogen sulfide, was detected in the astrocytoma cells in comparison to the neuroblastoma cells

Effect of S-Allyl -L-Cysteine on MCF-7 cell Line 3-mercaptopyruvate sulfurtransferase/sulfane sulfur system, viability and apoptosis

The S-Allyl-L-cysteine (SAC) component of aged garlic extract (AGE) is proven to have anticancer, antihepatotoxic, neuroprotective and neurotrophic properties. -Cystathionase (CTH), cystathionine -synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (MPST) are involved in H2S/sulfane sulfur endogenous formation from L-cysteine. The aim of the study was to determine the e ect of SAC on MCF-7 cells survival and apoptosis, which is a widely known approach to reduce the number of cancer cells. An additional goal of this paper was to investigate the e ect of SAC on the activity and expression of enzymes involved in H2S production. The experiments were carried out in the human breast adenocarcinoma cell line MCF-7. Changes in the cell viability were determined by MTT assay. Cell survival was determined by flow cytometry (FC). Changes in enzymes expression were analyzed using Western blot. After 24 h and 48 h incubation with 2245 M SAC, induction of late apoptosis was observed. A decrease in cell viability was observed with increasing SAC concentration and incubation time. SAC had no significant cytotoxic e ect on the MCF-7 cells upon all analyzed concentrations. CTH, MPST and CBS expression were confirmed in non-treated MCF-7 cells. Significant decrease in MPST activity at 2245 M SAC after 24 h and 48 h incubation vs. 1000 M SAC was associated with decrease in sulfane sulfur levels. The presented results show promising SAC e ects regarding the deterioration of the MCF-7 cells’ condition in reducing their viability through the downregulation of MPST expression and sulfate sulfur level reduction