Biomedical subjects

Etsuo Niki

Publications and source records attributed to Etsuo Niki.

At least 19 recordsLinked to original sources

PubMed2007

Acceleration of age-related changes in the retina in alpha-tocopherol transfer protein null mice fed a Vitamin E-deficient diet.

PURPOSE: To assess the role of vitamin E (VE) in age-related changes in the retinal tissues by using a mouse model of severe VE deficiency. METHODS: Pups of alpha-tocopherol transfer protein null (a-TTP(-)(/)(-)) mice were fed a VE-deficient diet for 4 or 18 months (VE (-) group). Wild-type C57BL/6 mice were fed a 0.002% alpha-tocopherol-supplemented diet (VE (+) group). In various ocular tissues, the VE levels were measured by high-performance liquid chromatography; the fatty acid composition by gas chromatography (GC); and the hydroxyoctadecadienoic acid and 8-iso-prostaglandin F(2)(alpha) levels, which are biomarkers for lipid peroxidation, by GC-mass spectrometry. The retinal structure was assessed by light, electron, and fluorescence microscopy. RESULTS: The alpha-tocopherol level in the retinas obtained from 4-month-old VE (-) animals was 71-fold lower than that in the retinas obtained from the VE (+) group. In addition, gamma-tocopherol was not detected; thus, the VE (-) group demonstrated a more severe VE deficiency than ever reported. In this group, the concentration of n-3 polyunsaturated fatty acids decreased (0.3- to 0.9-fold), whereas that of other classes of fatty acids was unchanged or increased. At 18 months of age, the number of the outer nuclear layer (ONL) nuclei was observed to be 17% lower in the VE (-) than in the VE (+) group (P < 0.05). Electron microscopy revealed larger amounts of matrix between the ONL nuclei indicating the Müller cell hypertrophy, greatly expanded rod outer segment discs, and a larger number of inclusion bodies in the retinal pigment epithelium (RPE; P < 0.05) in the VE (-) group. Fluorescence microscopy revealed that the autofluorescence signal was increased in the RPE layer in this group. When the observations of the 18-month-old animals were compared to those of the 4-month-old animals, the hydroxyoctadecadienoic acid and 8-iso-prostaglandin F(2)(alpha) levels were found to be increased in the retina and RPE obtained from both the VE (-) and VE (+) groups; however, the age-related increases were more remarkable in the VE (-) group (2.6- to 43.5-fold) than in the VE (+) group (0.8- to 8.7-fold). CONCLUSIONS: The combined use of a-TTP(-)(/)(-) mice and a VE-deficient diet leads to a severe deficiency of VE, enhances lipid peroxidation in the retina, and accelerates degenerative damage of the retina with age.

Animals↗

PubMed2006

17beta-estradiol protects cortical neurons against oxidative stress-induced cell death through reduction in the activity of mitogen-activated protein kinase and in the accumulation of intracellular calcium.

Although many studies have suggested that estrogen acts as a neuroprotective agent in oxidative stress, the underlying mechanism has not been fully elucidated. In the present study, we examined the effect of 17beta-estradiol (17beta-E2) on H(2)O(2)-induced death signaling in cultured cortical neurons. Exposure of the cortical neurons to H(2)O(2) triggered a series of events, including overactivation of p44/42 MAPK and intracellular Ca(2+) accumulation via voltage-gated Ca(2+) channels and ionotropic glutamate receptors, resulting in apoptotic-like cell death. The MAPK pathway might work as death signaling in our system, because the MAPK pathway inhibitor, U0126, blocked H(2)O(2)-induced MAPK activation, Ca(2+) overload, and cell death. Interestingly, a similar inhibitory effect on H(2)O(2)-triggered MAPK activation, Ca(2+) accumulation, and cell death was observed in cultures incubated with 17beta-E2 for 24 h before exposure to H(2)O(2), suggesting that the protective effect of 17beta-E2 is induced via attenuating overactivation of the MAPK pathway. Furthermore, we found that ionotropic glutamate receptor subunits, including NR2A and GluR2/3, but not NR2B and GluR1, were down-regulated in the 17beta-E2-treated cultures. The down-regulation of these glutamate receptor subunits was also observed after chronic treatment with U0126. Therefore, it is possible that 17beta-E2 down-regulates the expression of the ionotropic glutamate receptors by reducing activity of the MAPK pathway, which might be important for the protective effect of 17beta-E2 against oxidative stress-induced toxicity.

Animals↗

PubMed2006

Cytotoxic effects of various stressors on PC12 cells: involvement of oxidative stress and effect of antioxidants.

In order to specifically elucidate the involvement of oxidative stress, the effects of various types of stressors and antioxidants on PC12 cells were examined. In this study, the following four stressors were studied in detail: free radicals generated from 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH), 4-hydroxynonenal (HNE), 7-ketocholesterol (KC), and arsenic trioxide (As2O3). Undifferentiated PC12 cells were treated with 50% lethal concentration (LC50) of these stressors, and subsequently the viability, apoptosis/necrosis ratio, reactive oxygen species (ROS) production, caspase-3 activity, and protection by antioxidants were measured to elucidate the underlying mechanisms that determine the action of these stressors on PC12 cells. The cytotoxicity did not correlate directly with the intracellular formation of ROS. For example, as compared to AAPH, As2O3 produced considerably smaller amounts of ROS at LC50. As observed in the cells incubated with As2O3, KC and HNE exerted cell toxicity, but with a moderate production of ROS. With the exception of HNE, the apoptosis/necrosis ratio of all the stressors evaluated by annexin V and propidium iodide assays increased with an increase in the incubation time at the LC50 values of these stressors. In accordance with apoptosis ratio, caspase activity was detected in the cells incubated with AAPH, As2O3, and KC, but not HNE at LC50 for 24 h. The protective effect of alpha-tocopherol, 17beta-estradiol, 2,3-dihydro-5-hydroxy-2,2-dipentyl-4,6-di-tert-butylbenzofuran (BO653), glutathione, and N-acetylcysteine (NAC) against cytotoxicity depended on the type of stressors. These antioxidants were found to be effective against the abovementioned stressors, except As2O3 against which only NAC was effective. These results suggest that the involvement of ROS and the protective effect of antioxidants depend on the type of stressors.

Aldehydes↗

PubMed2006

Evaluation of the dietary effects of coenzyme Q in vivo by the oxidative stress marker, hydroxyoctadecadienoic acid and its stereoisomer ratio.

Coenzyme Q (CoQ) is an endogenous enzyme cofactor that may provide protective benefits as an antioxidant. In this study, in order to determine whether the concentrations of CoQ(9) are associated with the oxidative status in vivo, the effects of dietary supplements of CoQ(9) on mice were evaluated by using a new biomarker, total hydroxyoctadecadienoic acid (tHODE). Biological samples were first reduced and then saponified to convert the various oxidation products of linoleates to tHODE. Subsequently, by using GC-MS analyses, we simultaneously determined the absolute concentration of tHODE; its stereoisomer ratio, 9- and 13-(Z,E)-HODE/9- and 13-(E,E)-HODE, which is a measure of the hydrogen donor capacity of antioxidants; and the concentration of 8-iso-prostaglandin F(2alpha) (8-iso-PGF(2alpha)). Remarkable decreases in tHODE and 8-iso-PGF(2alpha) levels were observed in the plasma, erythrocytes, liver, and brain of mice that were maintained for 1 month on an alpha-tocopherol (alphaT)-free (E-free) diet supplemented with ubiquinone-9 (Q(9); 0.04 wt.%) as compared to those of mice that were fed an E-free diet. The (Z,E/E,E) HODE ratio was increased in the plasma and erythrocytes of mice that were fed a Q(9)-fortified diet as compared to those that were fed an E-free diet. In particular, the (Z,E/E,E) HODE ratios in the plasma and brain were significantly correlated with the concentrations of ubiquinol-9 (Q(9)H(2)). Further, the liver and brain levels of tHODE and 8-iso-PGF(2alpha) were significantly correlated with the plasma and erythrocyte levels of tHODE and 8-iso-PGF(2alpha), respectively, and in some cases, also exhibited significant correlations with antioxidants. These results indicate that the plasma and erythrocyte levels of tHODE and its stereoisomeric ratio can be prominent biomarkers for the evaluation of the oxidative status and antioxidant capacity in vivo, including in the liver and brain, and that CoQ plays a major role in the in vivo antioxidant network.

Alanine Transaminase↗

PubMed2006

gamma-Tocopherol attenuates MPTP-induced dopamine loss more efficiently than alpha-tocopherol in mouse brain.

Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mouse has been widely used as a rodent model of Parkinson's disease. In this study, alpha-tocopherol (alphaT) transfer protein knockout (heteromutant type, alpha-TTP((+/-))) mice were used to evaluate the protective effects of alphaT and gamma-tocopherol (gammaT) against MPTP-induced neurotoxicity. The intraperitoneal administration of MPTP to mice induced a decrease in the striatal levels of dopamine (DA) 3 days after the administration in both alpha-TTP((+/-)) and wild-type mice; these mice were fed an alphaT-deficient diet for 3 weeks before the MPTP administration. The DA levels in the alpha-TTP((+/-)) mice, which had been fed a gammaT-fortified diet (0.10 wt.%) for 3 weeks and were administered with MPTP, were recovered to those of the control, whereas there was no significant protective effect of alphaT despite the considerably higher striatal concentration of alphaT than gammaT. The immunohistochemical study also revealed that gammaT exerted a protective effect against neurodegenerative toxicity of MPTP. Collectively, this is the first report showing that the protective effect of gammaT is stronger than that of alphaT against the MPTP-induced damage of dopaminergic neurons in the mouse.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed2006

Induction of adaptive response and enhancement of PC12 cell tolerance by 7-hydroxycholesterol and 15-deoxy-delta(12,14)-prostaglandin J2 through up-regulation of cellular glutathione via different mechanisms.

Increasing evidence suggests an adaptive response induced by reactive oxygen species and other physiologically existing oxidative stimuli. We have recently reported that a variety of lipid peroxidation products at sublethal concentrations could induce adaptive response and enhance PC12 cell tolerance, although the detailed underlying molecular mechanisms have not been clearly clarified. In the present study, we found that both 7-hydroxycholesterol (7-OHCh) and 15-deoxy-delta(12,14)-prostaglandin J2 (15d-PGJ2) at sublethal concentrations significantly increased the cellular GSH as well as the enzyme activity of glutamate-cysteine ligase (GCL), the rate-limiting enzyme of GSH synthesis. Depletion of cellular GSH by buthionine sulfoximine completely abolished the adaptive response. Interestingly, treatment with 15d-PGJ2 significantly increased the gene expression of both subunits of GCL in an NF-E2-related factor 2 (Nrf2)-dependent manner, whereas neither 7-OHCh induced any considerable changes on the GCL gene expression nor did the Nrf2-small interfering RNA treatment exert any appreciable effects on the GSH elevation and subsequent adaptive response induced by 7-OHCh. These results demonstrate that the adaptive response induced by both 7-OHCh and 15d-PGJ2 is mediated similarly through the up-regulation of GSH but via different mechanisms.

Animals↗

PubMed2006

High-throughput nitric oxide assay in biological fluids using microchip capillary electrophoresis.

In order to develop a high-throughput screening method for the nitrogen monoxide metabolites, nitrite and nitrate, in biological fluids, we have investigated the simultaneous determination of these metabolites using microchip capillary electrophoresis (MCE). In this study, the control of applied voltage to obtain higher sensitivity by increasing the sample injection volume was investigated. Also, the improvement of reproducibility by correcting the injection volume using the internal standard was investigated. By increasing the sample volume, the limits of detection achieved for nitrite and nitrate were 24 and 12 microM, respectively. Because we used a 10-fold diluted sample when detecting nitrite and nitrate in human serum, it was necessary to increase the sensitivity by a factor of 10-50. The run-to-run and day-to-day relative standard deviations achieved were improved to less than 10% by using an internal standard to correct the injection volume. Moreover, we obtained successful separation of nitrite and nitrate in spiked human serum within 6.5 s under optimum analytical conditions. As a result, although it is necessary to obtain greater sensitivity, it was concluded that determination of the amount of NO metabolites in biological fluids using MCE is possible.

Calibration↗

PubMed2006

Detection of lipid peroxidation in light-exposed mouse retina assessed by oxidative stress markers, total hydroxyoctadecadienoic acid and 8-iso-prostaglandin F2alpha.

Exposure to excessive light induces retinal photoreceptor cell damage, which may involve lipid peroxidation. Morphological changes and the detection of internucleosomal DNA fragmentation confirmed the retinal damage caused by exposure of the retina of Balb/c mice to white fluorescent light (5000 lux, 2 h). The total amounts of hydroxyoctadecadienoic acid (tHODE) and 8-iso-prostaglandin F2alpha (8-iso-PGF2alpha) in the retinas obtained from light-exposed mice were assessed after reduction and saponification. In this method, both the free and ester forms of hydroperoxides, hydroxides, and ketones of linoleic acid are measured as tHODE by gas chromatography-mass spectrometry (GC-MS) analysis. When compared with controls, a significant increase in the concentrations of tHODE and 8-iso-PGF2alpha was observed 24 h after light exposure. Furthermore, the stereoisomeric ratio (Z,E)-HODE/(E,E)-HODE decreased after light exposure, suggesting the involvement of free-radical-mediated peroxidation. By the immunohistochemical technique, it was confirmed that 8-iso-PGF2alpha increased in the inner plexiform layer (IPL), outer plexiform layer (OPL), rod outer segment, and choroidal layer, while 13-HODE increased in the OPL and rod inner segment after light exposure. These results demonstrate that tHODE and 8-iso-PGF2alpha assessed by the present method are appropriate biomarkers responding to retinal photooxidative stress in vivo.

Animals↗

PubMed2006

Bio-markers of lipid peroxidation in vivo: hydroxyoctadecadienoic acid and hydroxycholesterol.

The biological role of lipid peroxidation products has continued to receive a great deal of attention not only for the elucidation of pathological mechanisms but also for their practical application to clinical use as bio-markers. In the last fifty years, lipid peroxidation has been the subject of extensive studies from the viewpoints of mechanisms, dynamics, product analysis, involvement in diseases, inhibition, and biological signaling. Lipid hydroperoxides are formed as the major primary products, however they are substrates for various enzymes and they also undergo various secondary reactions. In this decade, F2-isoprostanes from arachidonates and neuroprostanes from docosahexanoates have been proposed as bio-markers. Although these markers are formed by a free radical-mediated oxidation, the yields from the parent lipids are minimal. Compared to these markers, hydroperoxy octadecadienoates (HPODE) from linoleates and oxysterols from cholesterols are yielded by much simpler mechanisms from more abundant parent lipids in vivo. Recently, the method in which both free and ester forms of hydroperoxides and ketones as well as hydroxides of linoleic acid and cholesterol are measured as total hydroxyoctadecadienoic acid (tHODE) and 7-hydroxycholesterol (t7-OHCh), respectively, was proposed. The concentrations of tHODE and t7-OHCh determined by GC-MS analysis from physiological samples were much higher than that of 8-iso-prostagrandin F(2alpha). In addition to this advantage, hydrogen-donor activity of antioxidants in vivo could be determined by the isomeric-ratio of HODE (9- and 13-(Z,E)-HODE/9- and 13-(E,E)-HODE).

Animals↗

PubMed2006

Effective detection of peptides containing cysteine sulfonic acid using matrix-assisted laser desorption/ionization and laser desorption/ionization on porous silicon mass spectrometry.

Cysteine sulfonic acid-containing peptides, being typical acidic peptides, exhibit low response in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. In this study, matrix conditions and the effect of diammonium hydrogencitrate (DAHC) as additive were investigated for ionization of cysteine sulfonic acid-containing peptides in MALDI. A matrix-free ionization method, desorption/ionization on porous silicon (DIOS), was also utilized to evaluate the effect of DAHC. When equimolar three-component mixtures of peptides carrying free cysteine, cysteine sulfonic acid, and carbamidomethyl cysteine were measured by MALDI using a common matrix, alpha-cyano-4-hydroxycinnamic acid (CHCA), no signal corresponding to cysteine sulfonic acid-containing peptide could be observed in the mass spectrum. However, by addition of DAHC to CHCA, the peaks of cysteine sulfonic acid-containing peptides were successfully observed, as well as when using 2,4,6-trihydroxyacetophenone (THAP) and 2,6-dihydroxyacetophenone with DAHC. In the DIOS mass spectra of these analytes, the use of DAHC also enhanced the peak intensity of the cysteine sulfonic acid-containing peptides. On the basis of studies with these model peptides, tryptic digests of oxidized peroxiredoxin 6 were examined as a complex peptide mixture by MALDI and DIOS. In MALDI, the peaks of cysteine sulfonic acid-containing peptides were observed when using THAP/DAHC as the matrix, but this was not so with CHCA. In DIOS, the signal from cysteine sulfonic acid-containing peptides was suppressed; however, the use of DAHC significantly enhanced the signal intensity with an increase in the number of observed peptides and increased signal-to-noise ratio in the DIOS spectra. The results show that DAHC in the matrix or on the DIOS chip decreases discrimination and suppression effects in addition to suppressing alkali-adduct ions, which leads to a beneficial effect on protonation of peptides containing cysteine sulfonic acid.

Cysteine↗

PubMed2006

Lipid peroxidation in mice fed a choline-deficient diet as evaluated by total hydroxyoctadecadienoic acid.

OBJECTIVE: The relevance of oxidative stress in mice fed a choline-deficient diet (CDD) was investigated in relation to the oxidative stress marker, hydroxyoctadecadienoic acid (HODE) in comparison with F2-isoprostanes. Further, the protective effects of antioxidants against oxidative damage were assessed by using HODE. METHODS: We recently proposed total HODE as a biomarker for oxidative stress in vivo. Biological samples such as plasma, urine, and tissues were first reduced and then saponified to convert various oxidation products of linoleates to HODE. In the present study, this method was applied to measure oxidative damage in mice induced by CDD for 1 mo. RESULTS: CDD, when compared with choline-controlled diet (CCD), increased liver weight and fatty acid accumulation but the increase in body weight was less significant. Remarkable increases in HODE and 8-iso-prostaglandin F(2alpha) in liver and plasma were observed when mice were fed with the CDD for 1 mo compared with the CCD. The HODE level was about two to three orders higher than the F2-isoprostane level. This increase was decreased to the level of the CCD when alpha-tocopherol or 2,3-dihydro-5-hydroxy-4,6-di-tert-butyl-2,2-dipentylbenzofuran, a potent synthetic antioxidant, was mixed with the CDD. The stereoisomer ratio of HODE (9-and-13 (Z,E)-HODE/9-and-13 (E,E)-HODE) was decreased by CDD compared with CCD, which was spared by the addition of alpha-tocopherol and 2,3-dihydro-5-hydroxy-4,6-di-tert-butyl-2,2-dipentylbenzofuran. However, the increase in plasma glutamic-pyruvic transaminase and fatty acids in liver induced by the CDD was not recovered by any antioxidant. CONCLUSIONS: This study clearly demonstrated that oxidative stress was involved in fatty liver formation induced by the CDD and that HODE was a good biomarker for an oxidative stress in vivo.

Animals↗

PubMed2006

Turning point in apoptosis/necrosis induced by hydrogen peroxide.

The turning point between apoptosis and necrosis induced by hydrogen peroxide (H2O2) have been investigated using human T-lymphoma Jurkat cells. Cells treated with 50 microM H2O2 exhibited caspase-9 and caspase-3 activation, finally leading to apoptotic cell death. Treatment with 500 microM H2O2 did not exhibit caspase activation and changed the mode of death to necrosis. On the other hand, the release of cytochrome c from the mitochondria was observed under both conditions. Treatment with 500 microM H2O2, but not with 50 microM H2O2, caused a marked decrease in the intracellular ATP level; this is essential for apoptosome formation. H2O2-reducing enzymes such as cellular glutathione peroxidase (cGPx) and catalase, which are important for the activation of caspases, were active under the 500 microM H2O2 condition. Prevention of intracellular ATP loss, which did not influence cytochrome c release, significantly activated caspases, changing the mode of cell death from necrosis to apoptosis. These results suggest that ATP-dependent apoptosome formation determines whether H2O2-induced cell death is due to apoptosis or necrosis.

Adenosine Triphosphate↗

PubMed2006

Vitamin E protected cultured cortical neurons from oxidative stress-induced cell death through the activation of mitogen-activated protein kinase and phosphatidylinositol 3-kinase.

The role of vitamin E in the CNS has not been fully elucidated. In the present study, we found that pre-treatment with vitamin E analogs including alphaT (alpha-tocopherol), alphaT3 (alpha -tocotrienol), gammaT, and gammaT3 for 24 h prevented the cultured cortical neurons from cell death in oxidative stress stimulated by H2O2, while Trolox, a cell-permeable analog of alphaT, did not. The preventive effect of alphaT was dependent on de novo protein synthesis. Furthermore, we found that alphaT exposure induced the activation of both the MAP kinase (MAPK) and PI3 kinase (PI3K) pathways and that the alphaT-dependent survival effect was blocked by the inhibitors, U0126 (an MAPK pathway inhibitor) or LY294002 (a PI3K pathway inhibitor). Interestingly, the up-regulation of Bcl-2 (survival promoting molecule) was induced by alphaT application. The up-regulation of Bcl-2 did not occur in the presence of U0126 or LY294002, suggesting that alphaT-up-regulated Bcl-2 is mediated by these kinase pathways. These observations suggest that vitamin E analogs play an essential role in neuronal maintenance and survival in the CNS.

Animals↗

PubMed2005

Adaptive response induced by lipid peroxidation products in cell cultures.

The adaptive response induced by the lipid peroxidation products, such as phosphatidylcholine hydroperoxide, lysophosphatidylcholine (LysoPC), 15-deoxy-Delta(12,14)-prostaglandin J(2), 4-hydroxynonenal (4-HNE), hydroxyoctadecadienoic acid, 7-hydroxycholesterol, and cholesterol 5beta,6beta-epoxide, was investigated in this study. Although these products have been implicated in oxidative stress-related diseases, pretreatment with such compounds at sublethal concentrations significantly protected PC12 cells against subsequent oxidative stress induced by 6-hydroxydopamine. Moreover, 4-HNE and LysoPC also exhibited adaptive protection in human arterial endothelial cells. These findings suggest a general hormetic effect of such compounds in cell cultures and may lead to a reappraisal of the eventual role of reactive oxygen species and lipid peroxidation in organisms.

Adrenergic Agents↗

PubMed2005

4-Hydroxynonenal induces adaptive response and enhances PC12 cell tolerance primarily through induction of thioredoxin reductase 1 via activation of Nrf2.

4-Hydroxynonenal (4-HNE) is one of the major end products of lipid peroxidation. It has been widely accepted that 4-HNE can induce oxidative stress, implicating into extensive stress-related diseases. In the present study, however, 4-HNE was found to exert adaptive cytoprotective effect at low concentrations, which was primarily through induction of thioredoxin reductase 1 (TR1) via transcriptional activation of NF-E2-related factor 2 (Nrf2). Pretreatment with 4-HNE at sublethal concentrations significantly protected PC12 cells against the subsequent oxidative cell death induced by H2O2 and 6-hydroxydopamine. The cellular antioxidative glutathione system did not show any considerable changes, whereas the TR1 activity as well as the mRNA level was significantly elevated by the 4-HNE treatment. Cells treated with TR1 small interfering RNA exhibited less resistance to oxidative stress, and the adaptive response was completely abolished. The Nrf2 was transcriptionally activated by 4-HNE. Cells treated with Nrf2-small interfering RNA exerted lower constitutive levels of TR1 and exhibited less resistance to oxidative stress, and the 4-HNE-induced TR1 expression and subsequent adaptive response were again abolished in such cells. Treatment with 4-HNE at the adaptive concentration induced transient activation of extracellular signal-regulated protein kinase 1/2 and Akt/protein kinase B. Pharmacological inhibition of both these kinase pathways effectively attenuated 4-HNE-induced TR1 expression and subsequent adaptive protection. The above findings, taken together, suggest that stimulation with 4-HNE at sublethal concentrations induces adaptive response and enhances cell tolerance, primarily through induction of TR1 via transcriptional activation of Nrf2 signaling pathway, thereby protecting cells against the forthcoming oxidative stress.

Adaptation, Physiological↗

PubMed2005

Lipid peroxidation induced by carbon tetrachloride and its inhibition by antioxidant as evaluated by an oxidative stress marker, HODE.

We have recently proposed total hydroxyoctadecadienoic acid (HODE) as a biomarker for oxidative stress in vivo. The biological samples such as plasma, urine, and tissues were first reduced and then saponified to convert the oxidation products of linoleate to HODE. In the present study, this method was applied to measure the oxidative damage induced by the administration of carbon tetrachloride to mice and also to evaluate the capacity of antioxidant to inhibit the above damage. alpha-Tocopherol transfer protein knock out (alpha-TTP-/-) mice were used to evaluate antioxidant effect in the absence of alpha-tocopherol. The intraperitoneal administration of carbon tetrachloride to mice induced the increase in HODE in liver and plasma, which was followed by an increase in plasma glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT). F2-isoprostanes, another prevailing biomarker, were also increased similarly, but their concentration was approximately two to three orders of magnitude smaller than that of HODE. The lipophilic antioxidants such as gamma-tocopherol, gamma-tocotrienol and 2,3-dihydro-5-hydroxy-4,6-di-tert-butyl-2,2-dipentylbenzofuran (BO-653) were effective in suppressing the formation of HODE.

Alanine Transaminase↗

PubMed2005

Lipid peroxidation: mechanisms, inhibition, and biological effects.

In the last 50 years, lipid peroxidation has been the subject of extensive studies from the viewpoints of mechanisms, dynamics, product analysis, involvement in diseases, inhibition, and biological signaling. Lipids are oxidized by three distinct mechanisms; enzymatic oxidation, non-enzymatic, free radical-mediated oxidation, and non-enzymatic, non-radical oxidation. Each oxidation mechanism yields specific products. The oxidation of linoleates and cholesterol is discussed in some detail. The relative susceptibilities of lipids to oxidation depend on the reaction milieu as well as their inherent structure. Lipid hydroperoxides are formed as the major primary products, however they are substrates for various enzymes and they also undergo various secondary reactions. Phospholipid hydroperoxides, for example, are reduced to the corresponding hydroxides by selenoproteins in vivo. Various kinds of antioxidants with different functions inhibit lipid peroxidation and the deleterious effects caused by the lipid peroxidation products. Furthermore, the biological role of lipid peroxidation products has recently received a great deal of attention, but its physiological significance must be demonstrated in future studies.

Animals↗

PubMed2005

Adaptation to hydrogen peroxide enhances PC12 cell tolerance against oxidative damage.

The adaptive responses to H2O2 and the resulting protective effect against oxidative stress have been investigated using PC12 cells. Pretreatment of sublethal doses of H2O2 significantly protected PC12 cells against the cytotoxicity induced by lethal H2O2. The endogenous antioxidant defense systems, catalase and glutathione peroxidase, were enhanced quickly by the pretreatment of low doses of H2O2. This pretreatment also exerted protective effect against the oxidative insults induced by 6-hydroxydopamine and paraquat, but not against alkyl peroxyl radicals. Our results, taken together, suggest that the stimulation by low dose of H2O2 enriches the cellular antioxidant defense systems, thereby enhancing cell tolerance against the forthcoming oxidative insults induced by H2O2 and related hydroxyl radicals.

Adaptation, Physiological↗