Dual activation in oxidative coupling of 2-naphthols catalyzed by chiral dinuclear vanadium complexes

An efficient enantioselective oxidative coupling of 2-naphthol derivatives based on a concept of dual activation catalysis is realized. A chiral dinuclear vanadium(IV) complex (R_a,S,S)-1e possessing (S)-tert-leucine moieties at the 3,3′-positions of the (R)-binaphthyl skeleton was developed, which was found to promote the oxidative coupling of 2-naphthol to afford (S)-BINOL with 91% ee. To verify the dual activation mechanism, mononuclear vanadium(IV) complex (S)-8 was also prepared. Kinetic analysis revealed that the reaction rate of oxidative coupling of 2-naphthol promoted by (R_a,S,S)-1e is 48.3 times faster than that of (S)-8. The two vanadium metals in the chiral complex activate two molecules of 2-naphthol simultaneously in an intramolecular manner coupling reaction, achieving a high reaction rate with high enantiocontrol. Reaction mechanisms of the oxidative coupling reaction promoted by either vanadium(IV) or vanadium(V) complexes are also described.     

The effect of Lycium barbarum polysaccharide on alcohol-induced oxidative stress in rats

The aim of this study was to investigate the effects of Lycium barbarum polysaccharide (LBP) on alcohol-induced liver damage in rats. A total of 36 rats were divided into control, ethanol and ethanol + LBP groups. Rats in the ethanol group were fed 7 g ethanol/kg body weight by gastric infusion, three times a day, for 30 consecutive days, while rats in the control group received the same volume of physiological saline instead of ethanol, and rats in ethanol + LBP group were fed both ethanol (7 g/kg body weight) and LBP (300 mg/kg body weight/day). Alcoholic liver injury was examined by serum ALT and AST activities, alcoholic fatty liver was assessed by lipid levels, and oxidative stress was evaluated by SOD, CAT, GSH-Px, GSH and MDA assays. In the ethanol group, a significant elevation of enzymes and lipid in serum, increased MDA level and depletion of SOD, CAT, GSH-Px and GSH in liver were observed. LBP administration significantly ameliorated liver injury, prevented the progression of alcohol-induced fatty liver, and improved the antioxidant functions when compared with the ethanol group. Histopathological examination of rat liver revealed that LBP administration protected liver cells from the damage induced by ethanol. The results suggest that LBP is a promising agent to protect the liver from hepatotoxicity and fatty liver induced by ethanol intake.     

The effect of ultraviolet light on RNA metabolism in bromouracil deoxyriboside-grown HeLa cells

Abstract— The presence of 5-bromouracil deoxyriboside (BrUdR) in the DNA of HeLa cells has profound effects on RNA metabolism after u.v. irradiation. In normally grown cells 200 ergs/mm² depresses RNA synthesis by about 30 per cent while in BrUdR-grown cells the same exposure to u.v. depresses RNA synthesis by 95 per cent. When BrUdR-grown cells are u.v. -irradiated after being labeled with ³H-uridine, the normal autoradiographic pattern, where label shifts from nucleus to cytoplasm, fails to occur. Also, in lieu of the increase in RNA specific activity that is observed in unirradiated cells for a few hours after 20-min pulse-labeling, there occurs a constant decrease in specific activity after the irradiation.     

Sugar-dependent aggregation of glycoconjugated chlorins and its effect on photocytotoxicity in HeLa cells

In order to explore the influence of the sugar moieties of glycoconjugated chlorins on the photocytotoxicity, we studied the photochemical properties of four glycoconjugated chlorins in aqueous media such as cytoplasm and the concentration dependence of photocytotoxicity in HeLa cells. In phosphate-buffered saline, the fluorescence intensities of 5,10,15,20-tetrakis[3-(beta-D-glucopyranosyloxy)phenyl]chlorin (m-1a) and 5,10,15,20-tetrakis[3-(beta-D-galactopyranosyloxy)phenyl]chlorin (m-1b), i.e., chlorins having hexose groups, were about 2-fold greater than those of 5,10,15,20-tetrakis[3-(beta-d-xylopyranosyloxy)phenyl]chlorin (m-1c) and 5,10,15,20-tetrakis[3-(beta-d-arabinopyranosyloxy)phenyl]chlorin (m-1d), i.e., chlorins having pentose groups, owing to a sugar-dependent difference of aggregation behavior. While no cytotoxicity was found in the dark, the highest photocytotoxicity was shown by m-1a (82% inhibition) in HeLa cells. This was higher than those of m-1b, m-1c, m-1d and tetraphenylporphyrin tetrasulfonic acid. The glycoconjugated chlorins except for m-1b appeared to be distributed diffusely throughout the cytoplasm. Among the four photosensitizers, m-1a showed the highest intensity in confocal fluorescence images, in agreement with the in vitro photocytotoxicity results. For m-1c, no photocytotoxicity was found at drug concentrations from 0.2 to 0.04 microM. Hence, sugar-dependent aggregation is not the major reason for the unexpected lack of efficacy of m-1c, which is uptaken efficiently by HeLa cells. For the glycoconjugated chlorins, these results suggest the biological aspects of sugar moiety play much crucial role rather than chemical aspects.     

Protective effect of salidroside from Rhodiolae Radix on diabetes-induced oxidative stress in mice

It has been confirmed that diabetes mellitus (DM) carries increased oxidative stress. This study evaluated the effects of salidroside from Rhodiolae Radix on diabetes-induced oxidative stress in mice. After induction of diabetes, diabetic mice were administered daily doses of 50, 100 and 200 mg/kg salidroside for 28 days. Body weights, fasting blood glucose (FBG), serum insulin, TC (total cholesterol), TG (triglyceride), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT) were measured. Results showed that salidroside possessed hypoglycemic activity and protective effects against diabetes-induced oxidative stress, which could significantly reduce FBG, TC, TG and MDA levels, and at same time increase serum insulin levels, SOD, GPx and CAT activities. Therefore, salidroside should be considered as a candidate for future studies on diabetes.     

Regulation of oxidative stress inside living cells through polythiophene derivatives

Oxidative stress stimulated by angiotensin II(Ang II) plays an important role in the progression of inflammation and cardiovascular disease. In this work, polythiophene modified with dihydropyridine groups(PTDHP) realized the control of oxidative stress induced by Angiotensin II stimulation in living cells, by inhibiting the activity of NADPH oxidase via DHP groups. Upon light irradiation, the PTDHP could sensitize surrounding oxygen molecules to generate reactive oxygen species(ROS). The generated ROS oxidized the pendant DHP of polythiophene into pyridine group, which inactivated the control ability of DHP to oxidative stress in living cells. Thus, PTDHP can not only control the intracellular oxidative stress effectively and suppress ROS to some degree in dark, but also regulate its anti-oxidative effect under light irradiation.     

The effect of camphor and borneol on rat thymocyte viability and oxidative stress

Camphor and borneol are wildly distributed in the essential oils of medicinal plants from various parts of the World. Our study has been carried out to evaluate the effect of these two bicyclic monoterpenes on rat thymocytes. Camphor and borneol at concentrations of 0.5 and 5 μg/mL did not induce significant toxicity on the immune system cells, while a significant increase of thymocyte viability was detected when cells were incubated with 50 μg/mL of camphor. A significant increase of cell viability was similarly detected when thymocytes were cultivated with borneol at concentrations of 0.5 and 5 μg/mL. The role of camphor and borneol in reactive oxygen species (ROS) production and mitochondrial membrane potential (MMP) disturbances in rat thymocytes as well as their potential mechanism(s) of action were also discussed.     

Photodynamic effects of pterin on HeLa cells

Pterins, heterocyclic compounds widespread in biological systems, participate in relevant biological processes and are able to act as photosensitizers. In the present study, we ascertained that 2-aminopteridin-4(3H)-one, abbreviated as Ptr, is readily incorporated into and/or onto cervical cancer cells (HeLa) and that these cells die upon UV-A irradiation of Ptr. Cell death was assessed using two tests: (1) the Rhodamine 123 fluorescence assay for mitochondrial viability and (2) the Trypan Blue assay for membrane integrity. The data suggest that, for Ptr-dependent photoinitiated cell death, events related to mitochondrial failure precede those associated with the failure of the cell membrane.     

Protective effects of timosaponin BII on oxidative stress damage in PC12 cells based on metabolomics

Peroxide and oxygen free radicals are some of the causes of oxidative stress in brain tissue, and could lead to the change of brain structure and function. In addition, oxidative damage is one of the most important causes of the aging of the vast majority of tissues. The aim of this study is to investigate the protective effect of timosaponin BII on oxidative stress damage of PC12 induced by H₂O₂ using metabolomics based on the UHPLC‐Q‐TOF‐MS technique. Partial least‐squares discriminant analysis method was used to identify 35 metabolites as decisive marker compounds in a preliminary interpretation of the mechanism of the antioxidative effect of timosaponin BII. The majority of these metabolites are involved in the glutathione metabolism, amino acid metabolism, sphingolipid and glycerophospholipid metabolism. Our results suggest that timosaponin BII demonstrates systematic antioxidant effects in the PC12 oxidative damage cell model via the regulation of multiple metabolic pathways. These findings provide insight into the pathophysiological mechanisms underlying oxidative stress damage and suggest innovative and effective treatments for this disorder, providing a reliable basis for the development of novel therapeutic target in timosaponin BII treatment of oxidative stress.     

Using a TEMPO-based fluorescent probe for monitoring oxidative stress in living cells

Generation of too many reactive oxygen species (ROS) in relation to available antioxidants in living cells can cause oxidative stress, which is involved in the development and progression of several serious diseases. 2',7'-Dichlorodihydrofluorescein (DCFH) and its diacetate form, DCFH-DA, are widely used probes for monitoring general oxidative stress in cells, but DCFH oxidation is not always related to ROS. We report here a new method for quantifying cellular oxidative stress using a 2,2,6,6-tetramethyl- piperidine-1-oxyl (TEMPO)-based probe. We tested and verified the probe both in cell-free solutions and in living cells under conditions of increased or reduced oxidative stress. The probe revealed the oxidative stress status in living cells and may be a useful complement to DCFH fluorescent probes.     

Pseudolaric acid B induces apoptosis via activation of c-Jun N-terminal kinase and caspase-3 in HeLa cells

Pseudolaric acid B was isolated from Pseudolarix kaempferi Gordon (Pinaceae) and was evaluated for the anti-cancer effect in HeLa cells. We ob-served that pseudolaric acid B inhibited cell proliferation and induced apoptosis in a time- and dose-dependent manner. HeLa cells treated with pseudolaric acid B showed typical characteristics of apoptosis including the morphological changes and DNA fragmentation. JNK inhibitor, SP600125,markedly inhibited pseudolaric acid B-induced celldeath. In addition, Bcl-2 expression was down-regulated while Bax protein level was up-regulated.Caspase-3 inhibitor, z-DEVD-fmk, partially blocked pseudolaric acid B-induced cell death, and the expression of two classical caspase substrates,PARP and ICAD, were both decreased in a time-dependent manner, indicative of downstream cas-pase activation.     

Electrochemical detection in a microfluidic device of oxidative stress generated by macrophage cells

The release of reactive oxygen species (ROS) or reactive nitrogen species (RNS), i.e., the initial phase of oxidative stress, by macrophage cells has been studied by electrochemistry within a microfluidic device. Macrophages were first cultured into a detection chamber containing the three electrodes system and were subsequently stimulated by the microinjection of a calcium ionophore (A23187). Their production of ROS and RNS was then measured by amperometry at the surface of a platinized microelectrode. The fabricated microfluidic device provides an accurate measurement of oxidative release kinetics with an excellent reproducibility. We believe that such a method is simple and versatile for a number of advanced applications based on the detection of biological processes of secretion by a few or even a single living cell.     

Palladium-catalyzed oxidative activation of arylcyclopropanes

Palladium chloride-catalyzed intramolecular activation of electroneutral cyclopropane derivatives results in cleavage of the cyclopropane ring followed by formation of heterocyclic derivatives. Phenols, carboxylic acids, and amide groups were considered as substituents ortho to the cyclopropane ring in this catalytic activation chemistry. The regioselectivity observed in the case of amide-containing substrates was different from that of carboxylic acid-containing substrates, ruling out simple cyclopropane isomerization followed by a Wacker oxidation as the mechanistic pathway. [reaction: see text]     

HPLC-UV measurements of metabolites in the supernatant of endothelial cells exposed to oxidative stress

2,8-Dihydroxyadenine (2,8-DHA) was identified by high-performance liquid chromatography with ultraviolet detection as a major metabolite in the supernatant of endothelial cells of the pulmonary artery (PAECs) and aorta (AECs), in addition to hypoxanthine, xanthine, uric acid, and uracil. Under normoxic, hypoxic, and hyperoxic conditions, the concentrations of all the identified metabolites change with time, marking the response of endothelial cells to stress, as a result of changes in cellular metabolism. Thus, the metabolites can serve as stress markers, and their concentrations can indicate the type and the level of cell stress. The results verify that PAECs adapt to survive oxidative stress of hyperoxia. However, AECs can adapt to hypoxia only for a short time and do not survive prolonged hypoxia. The role of the polyamine synthesis pathway in the formation of the unsalvaged adenine, as a possible source of 2,8-DHA, is discussed.     

Adaptation of cyanobacteria to UV-B stress correlated with oxidative stress and oxidative damage

Cyanobacteria must cope with the negative effects of ultraviolet B (280-315 nm) (UV-B) stress caused by their obligatory light requirement for photosynthesis. The adaptation of the cyanobacterium Anabaena sp. to moderate UV-B radiation has been observed after 2 weeks of irradiation, as indicated by decreased oxidative stress, decreased damage, recovered photosynthetic efficiency and increased survival. Oxidative stress in the form of UV-B-induced production of reactive oxygen species was measured in vivo with the oxidative stress-sensitive probe 2',7'-dichlorodihydrofluorescein diacetate. Photooxidative damage by UV-B radiation, including lipid peroxidation and DNA strand breakage, was determined by a modified method using thiobarbituric acid reactive substances and fluorometric analysis of DNA unwinding. Photosynthetic quantum yield was determined by pulse amplitude-modulated fluorometry. The results suggest that moderate UV-B radiation results in an evident oxidative stress, enhanced lipid peroxidation, increased DNA strand breaks, elevated chlorophyll bleaching as well as decreased photosynthetic efficiency and survival during the initial exposure. However, DNA strand breaks, photosynthetic parameters and chlorophyll bleaching returned to their unirradiated levels after 4-7 days of irradiation. Oxidative stress and lipid peroxidation appeared to respond later because decreases were observed after 7 days of radiation. The survival curve against irradiation time exhibited a close relationship with the changes in photosynthetic quantum yield and DNA damage, with little mortality after 4 days. Growth inhibition by UV-B radiation was observed during the first 7 days of radiation, whereas normal growth resumed even under UV-B stress thereafter. An efficient defense system was assumed to come into play to repair photosynthetic and DNA damage and induce the de novo synthesis of UV-sensitive proteins and lipids, allowing the organisms to adapt to UV-B stress successfully and survive as well as grow. No induction of mycosporine-like amino acids (MAA) was observed during the adaptation of Anabaena sp. to UV-B stress in our work. The adaptation of the cyanobacterium correlated with and could be caused by the oxidative stress and oxidative damage.     

On the effect of stress on oxidative destruction of polymers. The action of ozone on polyolefines

A promoting effect of tensile stress has been revealed for the rate of oxidation of high- and low-density polyethylene and isotactic polypropylene films with ozone. The degree of oxidation and the presence of overstressed bonds on the sample surface were detected by infrared spectroscopy in transmitted and reflected light. Overstressed bonds on the surface were set up by using various quenching regimes and in the bulk by applying a load. The stress-induced changes in segmental mobility of macromolecules were studied by ESR spectroscopy using a stable nitroxyl radical-probe. Supramolecular structure of the samples was investigated by using birefringence, polarized infrared spectroscopy and X-ray diffraction methods. A substantial difference has been found between the stress and the strain dependences of the rate of oxidation of the polymer films with ozone.     

Cytoprotective effect of selenium polysaccharide from Pleurotus ostreatus against H2O2-induced oxidative stress and apoptosis in PC12 cells

One main fraction of Selenium-enriched Pleurotus ostreatus (P. ostreatus) polysaccharide (Se-POP-1) was extracted and purified by DEAE-52 and sephadex G-100. Se-POP-1 was an approximate homogenous polysaccharide with an average molecular weight of 1.62 × 10⁴ Da, and mainly composed of glucose, mannose and galactose, with molar ratio of 5.30:1.55:2.14. The absorption peaks at 941 cm^?1 and 1048 cm^?1 in FT-IR analysis were ascribed as C-O-Se and Se=O bonds. Pr-treatment of Se-POP-1 (400 μg/mL) increased the cell survival of H₂O₂-stimulated PC12 cells and inhibited intrinsic apoptosis and oxidative stress in H₂O₂-stimulated PC12 cells via limiting DNA degradation and decreasing the reactive oxygen species (ROS) generation. In addition, up-regulation of anti-apoptotic protein Bcl-2, down- regulation of pro-apoptotic protein Bax, cleaved caspase 3, and cytochrome c were also observed. Se-POP-1 presented an obvious effect to alleviate oxidative damage and apoptosis in PC12 cells induced by H₂O₂. Therefore, Se-POP-1 possessed potent antioxidant and biological activities with the ability to prevent oxidation via scavenging ROS and free radicals in cells. It could be developed as organic selenium dietary supplement and functional food.     

Arsenic-induced protein phosphorylation changes in HeLa cells

Arsenic is well documented as a chemotherapeutic agent capable of inducing cell death while at the same time is considered a human carcinogen and an environmental contaminant. Although arsenic toxicity is well known and has formed an impressive literature over the time, little is known about how its effects are exerted at the proteome level. Protein phosphorylation is an important post-translational modification involved in the regulation of cell signaling and likely is altered by arsenic treatment. Despite the importance of phosphorylation for many regulatory processes in cells, the identification and characterization of phosphorylation, as effected by arsenic through mass spectrometric detection, are not fully studied. Here, we identify phosphorylated proteins, which are related to post-translational modifications after phenylarsine oxide (PAO) inoculation to HeLa cells. PAO was chosen because of its high cytotoxicity, measured earlier in these labs. In this study, size exclusion chromatography coupled to inductively coupled plasma mass spectrometry (SEC-ICP-MS) is used to establish several molecular weight fractions with phosphorylated proteins by monitoring ³¹P signal vs. time via ICP-MS. SEC-ICP-MS fractions are collected and then separated by the nano-LC-CHIP/ITMS system for peptide determination. Spectrum Mill and MASCOT protein database search engines are used for protein identification. Several phosphorylation sites and proteins related to post-translational modifications are also identified.