Action of E. coli endotoxin,IL-1β and TNF-α on antioxidant status of cultured hepatocytes

We have previously reported that endotoxin induces in vivo oxidative stress in liver and a significant increase in hepatic and plasma glutathione concentrations during the acute phase of reversible endotoxic shock in rats. In the present study we examined the in vitro effects of E. coli 0111:B4 endotoxin (lipopolysaccharide, LPS), IL-1 and TNF- on antioxidant status of cultured hepatocytes in order to differentiate between the direct and mediated endotoxin action. LPS increased total glutathione (tGSH) levels after 2 h treatment but decreased oxidized glutathione (GSSG) content which lead to a marked decrease in GSSG/tGSH index. At shorter treatment times a biphasic and dose-dependent behaviour was observed. Cytokines (IL-1 and TNF-) produced significant decreases in tGSH and GSSG after 30 min treatment. Despite its prooxidant effect, TNF- significantly reduced GSSG/tGSH index. Although no significant effects were observed on glutathione reductase activity, both LPS and cytokines induced an important inhibition of glutathione peroxidase which can justify the lipid peroxidation previously observed both in liver during reversible endotoxic shock and in cultured hepatocytes after treatment with endotoxin. The inhibition of hepatic glutathione peroxidase, besides the stimulation of GSH synthesis by LPS and GSH efflux by cytokines, guarantees the export of hepatic glutathione in its reduced form for other organs, contributing to the interorgan homeostasis. On the other hand, the results presented here support a new role for GSSG/tGSH index different from a mere indicator of oxidative stress.     

Design, synthesis, and evaluation of an α-tocopherol analogue as a mitochondrial antioxidant

An efficient synthesis has provided access to a novel α-tocopherol analogue (2), as well as its trifluoroacetate salt and acetate ester. An annulation reaction was used to establish the pyridinol core structure and a Stille coupling reaction was employed for conjugation with the tocopherol side chain. This analogue was shown to suppress the levels of reactive oxygen species in cultured cells, and to quench peroxidation of mitochondrial membranes.     

Fluidity,permeability and antioxidant behaviour of model membranes incorporated with α-tocopherol and vitamin E acetate

Magnetic resonance studies reveal a marked difference between the binding of α-tocopherol and that of the corresponding acetate (vitamin E acetate) with dipalmitoylphosphatidylcholine (DPPC) vesicles. This is reflected in differences in the phase-transition curves of the DPPC vesicles incorporated with the two compounds, as well as in the ¹³C relaxation times and line widths. A model for the incorporation of these molecules in lipid bilayers has been suggested. α-Tocopherol binds strongly with the lipids, possibly through a hydrogen bond formation between the hydroxyl group of the former and one of the oxygen atoms of the latter. The possibility of such a hydrogen bond formation is excluded in vitamin E acetate, which binds loosely through the normal hydrophobic interaction. The model for lipid-vitamin interaction explains the in vitro decomposition of H₂O₂ by α-tocopherol. α-Tocopherol in conjuction with H₂O₂ can also act as a free-radical scavenger in the lipid phase. The incorporation of α-tocopherol and vitamin E acetate in DPPC vesicles enhances the permeability of lipid bilayers for small molecules such as sodium ascorbate.     

3,4,4′-Trihydroxy-trans-stilbene,an analogue of resveratrol,is a potent antioxidant and cytotoxic agent

Abstract

Resveratrol (3,5,4′-trihydroxy-trans-stilbene) is a naturally occurring polyphenol widely distributed in food and dietary plants. This phytochemical has been intensively studied as an efficient antioxidant and anticancer agent, and a variety of substituted stilbenes have been developed in order to improve the potency of resveratrol. In this work, we described the synthesis of 3,4,4 -trihydroxy-trans-stilbene (3,4,4′-THS), an analogue of resveratrol, and studied its antioxidant and cytotoxic activity in vitro. 3,4,4 -THS was much more efficient than resveratrol in protecting against free radical-induced lipid peroxidation, photo-sensitized DNA oxidative damage, and free radical-induced hemolysis of human red blood cells. More potent growth inhibition in cultured human leukemia cells (HL-60) was also observed for 3,4,4 -THS. The relationship between the antioxidant efficiency and cytotoxic activity was discussed, with the emphasis on inhibition of the free radical enzyme ribonucleotide reductase by antioxidants. The result that this subtle structure modification of resveratrol drastically improves its bioactivity provides important strategy to develop novel resveratrol-based molecules.     

The polyphenolic content of fruit and vegetables and their antioxidant activities. What does a serving constitute?

Analysis of the major flavone, flavonol, anthocyanidin and hydroxycinnamic acid constituents (and their glycosides) of onion, tomato, egg plant and apple has been undertaken and the antioxidant activities of the phenolic extracts determined. The major phenolic antioxidant components of egg plant are chlorogenic acid in the flesh and a delphinidin conjugate in the skin. In the case of apple, the major phenolic antioxidants detected are chlorogenic acid, procyanidins/catechin compounds, rutin and phloridzin. Quercetin glycosides are well-known to be the major phenolic components of onion. Assessment of the antioxidant activities of a serving of 100 g fresh weight fruit, vegetable and comparison with previously reported findings for 150 ml beverage (500 ml portion in the case of beer), expressed in μmol Trolox equivalents show that the antioxidant activities of 1 glass (150 ml) red wine ≡ 12 glasses white wine ≡ 2 cups of tea ≡ 4 apples ≡ 5 portions of onion ≡ 5.5 portions egg plant ≡ 3.5 glasses of blackcurrant juice ≡ 3.5 (500 ml) glasses of beer ≡ 7 glasses of orange juice ≡ 20 glasses of apple juice (long life).     

Alterations in the oxidation products,antioxidant markers,antioxidant capacity and lipid patterns in plasma of patients affected by Papillon-Lefèvre syndrome

Papillon-Lefèvre syndrome (PLS) is an uncommon disease. Less than 300 cases have been described. PLS is characterized by the association between palmar plantar hyperkeratosis (PPK) and severe precocious periodontitis that results in the premature loss of both the primary and secondary dentitions. It is known that periodontitis (PE), the destructive phase of periodontal disease, is a multifactor phenomenon involving a variety of molecular species, among them free radicals and reactive oxygen species (ROS). Antioxidants have been shown to play a critical role in modulating ROS-induced damages during PE. We wondered if patients belonging to a family group with different grades of PLS severity may present altered plasma concentrations of oxidation products as well as of lipophilic antioxidants, like Coenzyme Q or vitamin E, which are molecules that possess well-known antioxidant properties and could play a role in PE processes. We also wondered about the actual plasma total antioxidant capacity of these subjects as well as a complete identification of their plasma fatty acids features, which have been never investigated before. The results we obtained indicate an impairment in the antioxidant capacity of the subjects characterized by abnormally high hydroperoxide levels and, in some cases, by altered CoQ and vitamin E contents. Moreover, an essential fatty acid deficiency (EFAD) was registered on the basis of the peculiar plasma fatty acid patterns found (i.e. low PUFA, high MUFA and high delta-9 desaturase activity). This finding would support the hypothesisby Gutteridge and co-workers (Free Radic. Res. 1998, 28: 109-114) that conditions exist in which some forms of oxidative stress can lead to changes characteristic of EFAD.     

Antihyperglycemic and antioxidant effects of a flavanone, naringenin, in streptozotocin–nicotinamide-induced experimental diabetic rats

In the present study, the putative antihyperglycemic and antioxidant effects of a flavanone, naringenin, were evaluated in comparison with those of glyclazide, a standard drug for therapy of diabetes mellitus. Diabetes was induced experimentally in 12-h-fasted rats by intraperitoneal injections of first streptozotocin (50 mg/kg b.w.) and then of nicotinamide (110 mg/kg b.w.) after a 15-min interval. Untreated diabetic rats revealed the following in comparison with normal rats: significantly higher mean levels of blood glucose and glycosylated hemoglobin, significantly lower mean levels of serum insulin, significantly lower mean activities of pancreatic antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase), significantly lower mean levels of plasma non-enzymatic antioxidants (reduced glutathione, vitamin C , vitamin E), significantly elevated mean levels of pancreatic malondialdehyde (MDA) and significantly elevated mean activities of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH). Following oral administration of naringenin (50 mg/kg b.w./day) to diabetic rats for 21 days, the following observations were made in comparison with untreated diabetic rats: significantly lower mean levels of fasting blood glucose and glycosylated hemoglobin, significantly elevated serum insulin levels, significantly higher mean activities of pancreatic enzymatic antioxidants, significantly higher mean levels of plasma non-enzymatic antioxidants, lower mean pancreatic tissue levels of MDA and lower mean activities of ALT, AST, ALP and LDH in serum. The values obtained in the naringenin-treated animals approximated those observed in glyclazide-treated animals. Histopathological studies appeared to suggest a protective effect of naringenin on the pancreatic tissue in diabetic rats. These results suggest that naringenin exhibits antihyperglycemic and antioxidant effects in experimental diabetic rats.     

Release of β-galactosidase from E. coli by a plasmid containing a temperature sensitive lytic function

Summary We report the construction of a plasmid which carries the øX174 lysis gene E downstream from the lambda pL promoter. This plasmid is capable of triggering lysis inE. coli when the growth temperature is raised from 30°C to 42°C. The kinetics of release of -galactosidase and intracellular protein have been determined, as well as the decrease in cell viability upon induction of lysis. In addition, -galactosidase can be released efficiently after induction by a short sonication period. Both methods allow efficient release of -galactosidase.     

Phenethyl isothiocyanate,by virtue of its antioxidant activity,inhibits invasiveness and metastatic potential of breast cancer cells: HIF-1α as a putative target

Hypoxia-inducible factor 1α (HIF-1α) plays a crucial role in facilitating tumor progression and metastasis. Reducing the levels of HIF-1α might therefore be an important anticancer strategy. This could be achieved by understanding the key cellular events involved in HIF-1α activation. Present study explored the effect of phenethyl isothiocyanate (PEITC), a natural isothiocyanate, found in cruciferous vegetables on the expression of HIF-1α and HSP90 in breast adenocarcinoma cell lines (MCF-7 and MDA-MB-231) under both normoxia and hypoxia. This study established the possible role of ROS in the up-regulation of these markers in breast cancer cells. PEITC-induced nuclear accumulation of Nrf2, increased the activities of several antioxidant enzymes, and thus reduced the ROS burden of the tumor cells by acting as an indirect antioxidant. This resulted in the down-regulation of HSP90 and thereby HIF-1α expression. HSP90 was also found to be involved in the regulation of HIF-1α. A probable link between down-regulation of HIF-1α with reduction of ROS by PEITC through induction of Nrf2 was determined. Finally, our study demonstrated that modulation of HIF-1α by PEITC retarded adhesion, aggregation, migration and invasion of the breast cancer cells, thereby showing anti-metastatic effect. Activities of MMPs (2 & 9) and expression of VEGF were also altered by PEITC.