Toxicity of 1,2-dibromoethane in isolated hepatocytes: Role of lipid peroxidation

Treatment of isolated hepatocytes with 1,2-dibromoethane (DBE) caused a concentration dependent depletion of cellular glutathione (GSH) content and a parallel increase in the covalent binding of reactive intermediates to cell proteins, as a consequence of the haloalkane activation. The reduction of the hepatocyte GSH content, induced by DBE, stimulated the onset of lipid peroxidation, as measured by malondialdehyde (MDA) accumulation. N-Acetylcysteine (1 mM) was found to partially prevent GSH loss and to inhibit MDA formation, whereas equal concentrations of cysteine and methionine were ineffective on these respects. The stimulation of the peroxidative reactions appeared to be also associated with an increase in the leakage of lactate dehydrogenase (LDH) from the cells, indicative of a severe hepatocyte injury. Antioxidants such as -tocopherol, N,N′-phenyl-phenylenediamine (DPPD) and promethazine, as well as N-acetylcysteine reduced MDA formation to various extents and also protect against LDH release, yet without interfering with the covalent binding of DBE reactive intermediates to hepatocyte proteins. These results suggest the involvement of lipid peroxidation, consequent to GSH depletion, in the pathogenesis of liver cell necrosis due to DBE.     

Relationships between formaldehyde metabolism and toxicity and glutathione concentrations in isolated rat hepatocytes

The metabolism and toxicity of formaldehyde (CH2O) in isolated rat hepatocytes was found to be dependent upon the intracellular concentration of glutathione (GSH). Using hepatocytes depleted of GSH by treatment with diethyl maleate (DEM), the rate of CH2O (5.0 mM) disappearance was significantly decreased. Formaldehyde decreased the concentration of GSH in hepatocytes, probably by the extrusion of the CH2O-GSH adduct, S-hydroxymethylglutathione. Formaldehyde toxicity was potentiated in cells pretreated with 1.0 mM DEM as measured by the loss of membrane integrity (NADH stimulation of lactate dehydrogenase (LDH) activity) and an increase in lipid peroxidation (formation of thiobarbituric acid-reactive compounds). This potentiation of toxicity was both CH2O concentration-dependent and time-dependent. There was an excellent correlation between the increase in lipid peroxidation and the decrease in cell viability. L-Methionine (1.0 mM) both protected the cells from toxicity caused by the combination of 8.0 mM CH2O and 1.0 mM DEM and increased the cellular GSH concentration. The antioxidants, ascorbate, butylated hydroxytoluene (BHT) and alpha-tocopherol (10, 25 and 125 microM), all exhibited dose-dependent protection against toxicity produced by 8.0 mM CH2O and 1.0 mM DEM. At toxic concentrations of CH2O (10.0-13.0 mM), administered by itself, lipid peroxidation did not increase concomitantly with the decrease in cell viability and the addition of antioxidants (125 microM) did not influence CH2O toxicity. These results suggest that CH2O toxicity in GSH-depleted hepatocytes may be mediated by free radicals as a result of the effect of CH2O on a critical cellular pool of GSH. However, cells with normal concentrations of GSH are damaged by CH2O by a different mechanism.     

Activation and deactivation of aflatoxin B1 in isolated rat hepatocytes

To characterize the true substrate for aldolase from Clostridium perfringens (optimum pH = 7.2) several experiments were carried out wherein the substrate Neu5Ac was generated in situ at pH 5.4 by the action of sialidase on its substrate Neu5Ac(alpha, 2 leads to 3) lactose. The alpha-anomer formed in this reaction was found to be split by aldolase at this pH into ManNAc and pyruvate. beta-Neu5Ac as such was not converted at pH 5.4. However, when it was first mutarotated until the equilibrium mixture alpha:beta = 7.2:92.8 was obtained, it could be split. Inhibition experiments suggested that Neu5Ac was bound to the enzyme in a conformation that strongly resembled that of its alpha-anomer. The open chain form of ManNAc which arose after the action of aldolase preferentially formed the alpha-anomer followed by a fast mutarotation.     

Methionine metabolism and ultrastructural changes with D-galactosamine in isolated rat hepatocytes

The biochemical and morphological effects of 2, 10 and 100 mM of D-galactosamine (GalN) were studied in isolated rat hepatocytes during 2 h of incubation. Lactate dehydrogenase (LDH), alanine aminotransferase (ALAT) and cell viability did not change, whatever the concentration used. The variations observed, which were dose dependent, included a large drop in ATP levels and inhibition of RNA and protein synthesis. A very high concentration of GalN was necessary, however, to induce a significant decline in methionine adenosyltransferase activity compared to control cells.The use of L-[methyl-¹⁴C]methionine during cell incubation with GalN demonstrated a decrease of S-adenosyl-L-methionine (SAMe) and an accumulation of L-methionine content related to the GalN concentration. These results suggested that an hepatotoxic agent such as GalN was able to induce disturbances of methionine metabolism.Some of the ultrastructural changes observed were different from those previously found in vivo, in rats given GalN intraperitoneally, underlining the marked difference between in vivo and in vitro intoxication.     

Effect of metal ion catalyzed oxidation of rifamycin SV on cell viability and metabolic performance of isolated rat hepatocytes

The effect of rifamycin SV on metabolic performance and cell viability was studied using isolated hepatocytes from fed, starved and glutathione (GSH) depleted rats. The relationships between GSH depletion, nutritional status of the cells, glucose metabolism, lactate dehydrogenase (LDH) leakage and malondialdehyde (MDA) production in the presence of rifamycin SV and transition metal ions was investigated. Glucose metabolism was impaired in isolated hepatocytes from both fed and starved animals, the effect is dependent on the rifamycin SV concentration and is enhanced by copper (II). Oxygen consumption by isolated hepatocytes from starved rats was also increased by copper (II) and a partial inhibition due to catalase was observed. Cellular GSH levels which decrease with increasing the rifamycin SV concentration were almost depleted in the presence of copper (II). A correlation between GSH depletion and LDH leakage was observed in fed and starved cells. Catalase induced a slight inhibition of the impairment of gluconeogenesis, GSH depletion and LDH leakage in starved hepatocytes incubated with rifamycin SV, iron (II) and copper (II) salts. Lipid peroxidation measured as MDA production by isolated hepatocytes was also augmented by rifamycin SV and copper (II), especially in hepatic cells isolated from starved and GSH depleted rats. Higher cytotoxicity was observed in isolated hepatocytes from fasted animals when compared with fed or GSH depleted animals. It seems likely that in addition to GSH level, there are other factors which may have an influence on the susceptibility of hepatic cells towards xenobiotic induced cytotoxicity.     

Effects of subacute treatment of ethylene glycol on serum marker enzymes and erythrocyte and tissue antioxidant defense systems and lipid peroxidation in rats

The present study was aimed to investigate the effects of ethylene glycol (EG) on serum marker enzymes, antioxidant defense systems and lipid peroxidation concentration (malondialdehyde=MDA) in various tissues of rats exposed to ethylene glycol. EG (1.25% or 2.5%) in drinking water was administered orally to rats (Sprague-Dawley albino) ad libitum for 21 days continuously. EG treatments caused different effects on the serum marker enzymes, antioxidant defense system and MDA content in various tissues of the treatment groups as compared with the controls. EG also caused a significant increase in the serum marker enzyme activities with 2.5% dosage whereas, no changes were not observed with 1.25% dosage of EG treatment. Lipid peroxidation significantly increased in all the tissues except for in the heart and stomach of rats treated with both dosages of EG. Also, the antioxidative systems were also seriously affected by EG. For example, SOD significantly decreased in the liver treated with both dosages whereas, SOD activity in the erythrocytes, kidney, heart and stomach were significantly increased and not changed in the brain with two dosages of EG. Also, while CAT activity significantly decreased in the erythrocytes, liver and kidney, the activity in the stomach significantly increased, but did not change in the brain and heart with two doses of EG. GR activity significantly decreased in the erythrocytes treated with both dosages of EG whereas GR was not affected in other tissues by EG treatment. GST activity significantly elevated in the heart and brain but did not change in the other tissues of rats treated with both dosages of EG. Meanwhile, GSH depletion in the erythrocytes of rats treated with 2.5% dosage of EG was found to be significant whereas, the level of GSH in the brain was significantly increased treated with both the dosages of EG. The observations presented led us to conclude that the administration of subacute EG promotes lipid peroxidatin content, elevates tissue damage serum marker enzymes and changes in the antioxidative systems in rats. These data, along with the determined changes suggest that EG produced substantial systemic organ toxicity in the erythrocyte, liver, brain, heart kidney and stomach during the period of a 21-day subacute exposure.     

Comparative reactivities of various biological compounds with myeloperoxidase-hydrogen peroxide-chloride,and similarity of oxidant to hypochlorite

The reactivities of myeloperoxidase-H₂O₂-Cl^? and sodium hypochlorite with amino acids, uric acid, NADH, ascorbic acid, ADP, albumin, haemoglobin, α₁-antitrypsin and some hydroxyl radical scavengers have been compared. The ability of each compound to inhibit chlorination of monochlorodimedon by both oxidants was measured. Relative reaction rates varied over a range of 10⁵, but the reactivities of the two oxidants with each compound were very similar, from which it is concluded that the reactions of hypochlorite accurately reflect those of the myeloperoxidase system. Thiol compounds (cysteine and GSH) and methionine were more than 100-times more reactive than other amino acids, which had comparable reactivity to NADH and uric acid. Benzoate, dimethylsulphoxide and formate were very much less reactive. The significance of these reactions of myeloperoxidase in microbial killing and inflammation is discussed.     

The protective action of glutathione on the microbial mutagenicity of the Z- and E-isomers of 1,3-dichloropropene

The Z(cis)- and E(trans)-isomers of 1,3-dichloropropene (DCP), in confirmation of previous reports, caused dose-dependent increases in the numbers of reverse mutations in Salmonella typhimurium TA100 in the presence and absence of a 9000 X g supernatant fraction (S9) from the livers of Aroclor-treated rats. The relevance of these findings to mammals is uncertain, not least because of major differences in the metabolism of the DCPs in the microbial assay systems and in vivo. For example, (Z)-DCP is efficiently detoxified in mammals by the operation of a glutathione (GSH)-dependent S-alkyl transferase. It is possible that such detoxification could proceed only very slowly in the microbial assays because the concentrations of GSH could be severely rate-limiting even in those assays fortified by the addition of S9. The results obtained in the current study demonstrate a dramatic reduction in the microbial mutagenicity of both (Z)- and (E)-DCP when the concentration of GSH in the microbial assays was adjusted to a normal physiological concentration (5 mM). However, this protective action of GSH was at least as effective in the absence of S9 as in its presence, suggesting that it was not mediated by mammalian GSH transferase. There appears to be little or no GSH alkyl or aryl transferase in the cytosol of S. typhimurium TA100, but intracellular GSH is present at a concentration similar to that found in mammalian cells. Since the uncatalysed reaction between the DCPs and glutathione is relatively slow, the effect is not due simply to their destruction by GSH. It is possible that a physiological concentration of extracellular GSH maintains the intracellular GSH in a reduced form in which its nucleophilic thiol group competes effectively with the nucleophilic centres in the bacterial DNA for the haloalkenes. The current results highlight the efficiency of GSH-linked systems in affording protection against the genotoxic action of the DCPs. It may be presumed that their operation would exert a major limiting effect on the genotoxicity of (Z)- and (E)-DCP in mammals.     

Measurement of drug-metabolizing systems in Salmonella typhimurium strains G46, TA1535, TA100, TA1538 and TA98

Salmonella typhimurium strains which are commonly used in the Ames test for screening potential carcinogens were examined for a number of drug-metabolizing systems. Neither cytochrome P-450 itself nor two activities catalyzed by the cytochrome P-450 system in mammalian cells, i.e., benzpyrene monooxygenase and ethoxycoumarin O-deethylation, could be detected. Nor do these bacterial strains demonstrate any ability to detoxify epoxides by hydrating them or to conjugate p-nitrophenol with glucuronic acid.On the other hand, S. typhimurium strains G46, TA1535, TA100, TA1538 and TA98 contain considerable amounts of acid-soluble thiols, approx. 5–10% of which is glutathione. These bacteria can also enzymatically conjugate glutathione with 1-chloro-2,4-dinitrobenzene (CDNB) and can reduce oxidized glutathione using NADPH as cofactor.Thus, enzymatic and non-enzymatic reaction of immediate carcinogens with thiol groups in S. typhimurium may have a significant effect on the outcome of the Ames test in certain cases.     

A Comparison of the Effects of Ocular Preservatives on Mammalian and Microbial ATP and Glutathione Levels

The aim of this study was to investigate the mechanism of action of the preservative sodium chlorite (NaClO²), and the relationship with intracellular glutathione depletion. A detailed comparison of the dose responses of two cultured ocular epithelial cell types and four species of microorganism was carried out, and comparisons were also made with the quaternary ammonium compound benzalkonium chloride (BAK), and the oxidant hydrogen peroxide (H²O²). The viability of mammalian and microbial cells was assessed in the same way, by the measurement of intracellular ATP using a bioluminescence method. Intracellular total glutathione was measured by reaction with 5,5′-dithiobis-2-nitrobenzoic acid in a glutathione reductase-dependent recycling assay. BAK and H²O² caused complete toxicity to conjunctival and corneal epithelial cells at ～25?ppm, in contrast to NaClO², where >100?ppm was required. The fungi Candida albicans and Alternaria alternata had a higher resistance to NaClO² than the bacteria Staphyloccus aureus and Pseudomonas aeruginosa, but the bacteria were extremely resistant to H²O². NaClO² caused substantial depletion of intracellular glutathione in all cell types, at concentrations ranging from <10?ppm in Pseudomonas, 25–100?ppm in epithelial cells, to >500?ppm in fungal cells. The mechanisms of cytotoxicity of NaClO², H²O² and BAK all appeared to differ. NaClO² was found to have the best balance of high antibacterial toxicity with low ocular toxicity. The lower toxicity of NaClO² to the ocular cells, compared with BAK and H²O², is in agreement with fewer reported adverse effects of application in the eye.     

Arachidonic acid converts the glutathione depletion-induced apoptosis to necrosis by promoting lipid peroxidation and reducing caspase-3 activity in rat glioma cells

Intracellular glutathione (GSH) depletion induced by buthionine sulfoximine (BSO) caused cell death that seemed to be apoptosis in C6 rat glioma cells. Arachidonic acid (AA) promoted BSO-induced cell death by accumulating reactive oxygen species (ROS) or hydroperoxides. AA inhibited caspase-3 activation and internucleosomal DNA fragmentation during the BSO-induced GSH depletion. Furthermore, AA reduced intracellular ATP content, induced dysfunction of mitochondrial membrane and enhanced 8-hydroxy-2'-deoxyguanosine (8-OH-dG) production. There was significant increase of 12-lipoxygenase activity in the presence of AA under the BSO-induced GSH depletion in C6 cells. These results suggest that AA promotes cell death by changing to necrosis from apoptosis through lipid peroxidation initiated by lipid hydroperoxides produced by 12-lipoxygenase under the GSH depletion in C6 cells. Some ROS such as hydroperoxide produced by unknown pathway make hydroxy radicals and induce 8-OH-dG formation in the cells. The conversion of apoptosis to necrosis may be a possible event under GSH depleted conditions.     

In vitro Interactions of Thallium with Components of the Glutathione-dependent Antioxidant Defence System

We investigated the hypothesis that thallium (Tl) interactions with the glutathione-dependent antioxidant defence system could contribute to the oxidative stress associated with Tl toxicity. Working in vitro with reduced glutathione (GSH), glutathione reductase (GR) or glutathione peroxidase (GPx) in solution, we studied the effects of Tl⁺ and Tl³⁺ (1-25 μM) on: (a) the amount of free GSH, investigating whether the metal binds to GSH and/or oxidizes it; (b) the activity of the enzyme GR, that catalyzes GSH regeneration; and (c) the enzyme GPx, that reduces hydroperoxide at expense of GSH oxidation. We found that, while Tl⁺ had no effect on GSH concentration, Tl³⁺ oxidized it. Both cations inhibited the reduction of GSSG by GR and the diaphorase activity of this enzyme. In addition, Tl³⁺per se oxidized NADPH, the cofactor of GR. The effects of Tl on GPx activity depended on the metal charge: Tl⁺ inhibited GPx when cumene hydroperoxide (CuOOH) was the substrate, while Tl³⁺-mediated GPx inhibition occurred with both substrates. The present results show that Tl interacts with all the components of GSH/GSSG antioxidant defence system. Alterations of this protective pathway could be partially responsible for the oxidative stress associated with Tl toxicity.     

tert–butylhydroperoxide—Induced toxicity in isolated hepatocytes: Contribution of thiol oxidation and lipid peroxidation

Incubation of isolated rat hepatocytes with tert-butylhydroperoxide resulted in marked cytotoxicity preceded by intracellular glutathione depletion and extensive lipid peroxidation. Addition of antioxidants delayed, but did not prevent, this toxicity. A significant decrease in protein-free sulfhydryl groups also, occurred in the presence of tert-butylhydroperoxide; direct oxidation of protein thiols and mixed disulfide formation with glutathione were responsible for this decrease. The involvement of protein thiol depletion in tert-butylhydroperoxide–induced cytotoxicity is suggested by our observation that administration of dithiothreitol, which caused re-reduction of the oxidized sulfhydryl groups and mixed disulfides, efficiently protected the cells from toxicity. Moreover, depletion of intracellular glutathione by pretreatment of the hepatocytes with diethyl maleate accelerated and enhanced the depletion of protein thiols induced by tert-butylhydroperoxide and potentiated cell toxicity even in the absence of lipid peroxidation.     

Chemically induced antioxidant-sensitive respiration. Relation to glutathione content and lipid peroxidation in the perfused rat liver

The interrelations between the hepatic chemically induced antioxidant-sensitive respiration and the contents of malondialdehyde (MDA) and of reduced glutathione (GSH), were studied in the isolated hemoglobin-free perfused rat liver. Antioxidant-sensitive respiration was induced by the infusion of agents such as ethanol, iron, xanthine or t-butyl hydroperoxide, or by phenylhydrazine pretreatment in vivo. The development of this respiratory component occurred concomitantly with high levels of MDA in the perfused livers, while those of GSH were diminished.     

Biotransformation and cytotoxic effects of hydroxychavicol, an intermediate of safrole metabolism, in isolated rat hepatocytes

The biotransformation and cytotoxic effects of hydroxychavicol (HC; 1-allyl-3,4-dihydroxybenzene), which is a catecholic component in piper betel leaf and a major intermediary metabolite of safrole in rats and humans, was studied in freshly isolated rat hepatocytes. The exposure of hepatocytes to HC caused not only concentration (0.25-1.0 mM)- and time (0-3 h)-dependent cell death accompanied by the loss of cellular ATP, adenine nucleotide pools, reduced glutathione, and protein thiols, but also the accumulation of glutathione disulfide and malondialdehyde, indicating lipid peroxidation. At a concentration of 1 mM, the cytotoxic effects of safrole were less than those of HC. The loss of mitochondrial membrane potential and generation of oxygen radical species assayed using 2′,7′-dichlorodihydrofluoresein diacetate (DCFH-DA) in hepatocytes treated with HC were greater than those with safrole. HC at a weakly toxic level (0.25 and/or 0.50 mM) was metabolized to monoglucuronide, monosulfate, and monoglutathione conjugates, which were identified by mass spectra and/or ¹H nuclear magnetic resonance spectra. The amounts of sulfate rather than glucuronide or glutathione conjugate predominantly increased, accompanied by a loss of the parent compound, with time. In hepatocytes pretreated with either diethyl maleate or salicylamide, HC-induced cytotoxicity was enhanced, accompanied by a decrease in the formation of these conjugates and by the inhibition of HC loss. Taken collectively, our results indicate that (a) mitochondria are target organelles for HC, which elicits cytotoxicity through mitochondrial failure related to mitochondrial membrane potential at an early stage and subsequently lipid peroxidation through oxidative stress at a later stage; (b) the onset of cytotoxicity depends on the initial and residual concentrations of HC rather than those of its metabolites; (c) the toxicity of HC is greater than that of safrole, suggesting the participation of a catecholic intermediate in safrole cytotoxicity in rat hepatocytes.     

Spinacia oleracea L. protects against gamma radiations: a study on glutathione and lipid peroxidation in mouse liver

The present study deals with the protective effect of Spinacia oleracea L. against radiation-induced oxidative stress, which is evaluated in terms of lipid peroxidation (LPO) product and tissue levels of glutathione. Swiss albino male mice aged 6–8 weeks, weighing 22±3 g, each were selected from an inbred colony and divided into four groups. One group served as normal and a second group (extract of S. oleracea L. (SE) treated un-irradiated) were administered methanolic (50%) SE at a dose of 1100 mg/kg body wt./day dissolved in distilled water. A third group (untreated-irradiated) was administered distilled water orally, which served as control. A fourth group (SE pre-treated irradiated) was administered methanolic (50%) SE at a dose of 1100 mg/kg body wt./day dissolved in distilled water. Two groups, one untreated-irradiated and another S. oleracea pre-treated irradiated were exposed to 5 Gy of gamma radiation at a rate of 1.07 Gy/min with a source-to-surface distance of 77.5 cm. The animals were autopsied at 1, 3, 7, 15, and 30 days post-exposure. LPO increased after irradiation up to day 15 in the untreated-irradiated group and up to day 7 in SE pre-treated irradiated mice. LPO values were significantly lower in the SE pre-treated irradiated group as compared to their respective untreated-irradiated group at all intervals, which reached normal values from day 7 onward. The percentage of protection observed in the SE pre-treated irradiated group was, 22.22%, 24.8%, 33.25%, 42.84% and 26.36% at 1, 3, 7, 15, 30 days post-exposure, respectively. Radiation-induced glutathione depletion was checked after 7 days’ exposure in SE pre-treated irradiated as compared to untreated-irradiated in which recovery started after day 15. Values were significantly higher in the SE pre-treated irradiated group from their respective untreated-irradiated group at all intervals. The percentage of protection observed in the SE pre-treated irradiated group was, 29.41%, 42.68%, 43.55%, 53.81%, 39.28% at 1, 3, 7, 15, 30 days post-exposure, respectively. It is found that radiation-induced augmentation in malondialdehyde contents and depletion in glutathione changes in liver can be altered by S. oleracea L. The protection may be attributed to the combined effects of its constituents rather than to any single factor as the leaves are rich in carotenoid content (β-carotene, lutein, Zeaxanthine), ascorbic acid, flavonoids and p-coumaric acid. Thus Spinacia, showing protection in liver, may prove promising as a rich source of antioxidants because its use is cost-effective, especially for peoples in adverse and hazardous circumstances who are living in poverty.     

Biological and methodological implications of prostaglandin involvement in mouse brain lipid peroxidation measurements

Enhanced cyclooxygenase-mediated prostaglandin (PG) turnover occurring during sacrifice and biochemical processing of tissues also generates malondialdehyde (MDA), a product of lipid peroxidation (LPO). Studies reporting on LPO estimated by thiobarbituric acid reactive substances (TBARS) have failed to consider such artefactual increases. This study reports the relative proportion of PG metabolism-derived MDA (PG-MDA) in mouse brain regions during the TBARS assay. The cyclooxygenase inhibitor indomethacin significantly lowered MDA in fronto-parietal cortex and corpus striatum. Indomethacin (50–800 g/ml, in vitro) increased estimated TBARS in whole brain. Such enhancement was absent when indomethacin (20–80 g/sample) was added to the MDA standard curve, reflecting its interaction with TBARS other than MDA. PG-MDA contributes as much as 15% to the total estimated value of MDA in fronto-parietal cortex and corpus striatum and must be corrected for in LPO studies.     

Glutathione and glutathione S-transferases in the salmonella mammalian-microsome mutagenicity test

Levels of the tripeptide glutathione (GSH) and the activity of glutathione S-transferases were investigated in S9 fractions of rats and mice and in Salmonella typhymurium tester strains TA1535, TA100, TA1538 and TA98. The S9 and Salmonella typhimurium tester strains had high levels of glutathione. Compared with S9, the activity of GSH S-transferases was lower in the bacteria. However, electrophiles such as 1-chloro-2,4-dinitrobenzene (CDNB), diethyl maleate and styrene oxide were effectively bound to bacterial GSH.

The mutagenicity of the direct mutagen CDNB was drastically lowered in presence of S9 fractions but not in presence of microsomes. A comparable decrease was obtained when microsomal supernatant, which contains GSH and GSH S-transferases, was added to the microsomes. Addition of GSH in excess completely abolished mutagenicity of CDNB. These results demonstrate that the conjugation of electrophiles with GSH mediated by the S9 fraction or the bacterial tester strains represents an important detoxication mechanism which may influence the results obtained with the Salmonella typhimurium mammalian-microsome mutagenicity test.     

The role of resveratrol and melatonin in the nitric oxide and its oxidation products mediated functional and structural modifications of two glycolytic enzymes: GAPDH and LDH

Background

Nitric oxide is a well-known gaseous signaling molecule and protein modifying agent. However, at higher concentrations or during oxidative stress nitric oxide may exert some deleterious effects on protein structure and function. Here we investigated the influence of nitric oxide and products of its oxidation on two glycolytic enzymes: GAPDH and LDH under in vitro nitrosative stress conditions. Secondly, we applied natural antioxidants: melatonin and resveratrol to examine their effects on the enzymes under studied conditions.