Product Of Membrane Lipid Peroxidation Research Articles

Cocoa procyanidins attenuate 4-hydroxynonenal-induced apoptosis of PC12 cells by directly inhibiting mitogen-activated protein kinase kinase 4 activity

Neurodegenerative disorders such as Alzheimer's disease (AD) are associated with oxidative stress, and it has been suggested that apoptosis is a crucial pathway in neuronal cell death in AD patients. 4-Hydroxynonenal (HNE), one of the aldehydic products of membrane lipid peroxidation, is reported to be elevated in the brains of AD patients and mediates the induction of neuronal apoptosis in the presence of oxidative stress. In this study, we investigated the HNE-induced apoptosis mechanism and the protective effects of the cocoa procyanidin fraction (CPF) and its major antioxidant procyanidin B2 against the apoptosis induced by HNE in rat pheochromocytoma (PC12) cells. HNE-induced nuclear condensation and increased sub-G1 fraction, both of which are markers of apoptotic cell death, were inhibited by CPF and procyanidin B2. Intracellular reactive oxygen species (ROS) accumulation was attenuated by pretreatment with CPF and procyanidin B2. CPF and procyanidin B2 also prevented HNE-induced poly(ADP-ribose) polymerase cleavage, antiapoptotic protein (Bcl-2 and Bcl-X L) down-regulation, and caspase-3 activation. Activation of c-Jun N-terminal protein kinase (JNK) and mitogen-activated protein kinase kinase 4 (MKK4) was attenuated by CPF and procyanidin B2. Moreover, CPF and procyanidin B2 bound directly to MKK4 and inhibited its activity. Data obtained with SP600125, a selective inhibitor of JNK, revealed that JNK is involved in HNE-induced apoptosis through the inhibition of PARP cleavage and caspase-3 activation in PC12 cells. Collectively, these results indicate that CPF and procyanidin B2 protect PC12 cells against HNE-induced apoptosis by blocking MKK4 activity as well as ROS accumulation.

Melatonin: Quantum-chemical and biochemical investigation of antioxidant activity

Experimental and theoretical investigation of the antioxidant activity of melatonin is carried out. The theoretical approach comprises the evaluation of several appropriate descriptors of scavenging activity with the help of quantum-chemistry methods. The values obtained are compared with available data for substances with established antioxidant properties. One of the most widely used markers for in vivo free radical oxidation processes is malondialdehyde (MDA) as an end product of membrane lipid peroxidation. Experimental support of the computed scavenging parameters is provided by estimation of the effect of supplementary melatonin therapy on the plasma levels of MDA in CRF patients on maintenance HD therapy. Different reaction paths have been considered and related to the obtained data, allowing speculations about the reaction mechanism and the antioxidant potential of melatonin for practical purposes.

Induction of the activities of antioxidative enzymes and the levels of malondialdehyde in cucumber seedlings as a consequence of Bemisia tabaci (Hemiptera: Aleyrodidae) infestation

The activities of antioxidative enzymes and the concentration of malondialdehyde were assayed in cucumber leaves (Cucumis sativus L.) 0, 6, 12, 24, 48, 72, and 96 h after the cucumber seedlings were infested by Bemisia tabaci (Gennadius). The results indicated that the activities of antioxidative enzymes were increased after herbivore infestation, including superoxide dismutase (SOD), and peroxidase (POD), and the levels of malondialdehyde (MDA), which is a product of membrane lipid peroxidation in the leaves. The enzymes and MDA showed peaks of different activity levels at 24 and 48 h after the infestation. SOD activity reached the highest peak, 10.4% higher than control, at 24 h, POD activity reached the highest peak, 213.2% higher than control, at 6 h, catalase (CAT) activity was not statistically significant compared with the control, and MDA content reached the highest peak, 59.9% higher than control, at 48 h. The results suggested that the enhanced activities of antioxidative enzymes and MDA content may contribute to bioprotection of cucumber plants against B. tabaci infestation.

Proline involvement in the common sage antioxidant system in the presence of NaCl and paraquat

To elucidate proline antioxidant properties in common sage (Salvia officinalis L.) plants, they were treated with paraquat (a producer of superoxide radical) and/or NaCl and also with paraquat and proline at the stage of 4–5 true leaves. The paraquat solution (1 ml containing 0.1 μmol of the agent) was applied to the leaf surface; NaCl (200 mM) and proline (the final concentration of 5 mM) were added to nutrient medium. Experimental plants were firstly kept in darkness for 12 h, then illuminated, and in 3, 6, and 12 h, leaves and roots were fixed for biochemical analyses. The results obtained are in agreement with the supposition of proline antioxidant properties. In particular, it was established that paraquat induced a slight increase in the proline level in the leaves during dark period of plant growth and also during subsequent 3 h after light switching on. This transient proline accumulation in the leaves was accompanied by its level decrease in the roots. Proline addition to the nutrient medium of paraquat-treated plants neutralized paraquat damaging action on the leaves. In the presence of paraquat, proline treatment reduced the accumulation in the roots of hydrogen peroxide and malondialdehyde, the product of membrane lipid peroxidation. It also affected indirectly the activities of superoxide dismutase (SOD) and free, covalently bound, and ionically bound peroxidases. Keeping in mind that, in the presence of paraquat, superoxide-induced changes in SOD activity in the roots were negatively correlated with the level of proline, which content was the highest during the last hours of experiments, we can conclude that proline antioxidant effects are manifested only after 12 h of stressor action, whereas antioxidant enzymes are involved in ROS scavenging during the earlier stage of damaging factor action.

Toll-like receptor-4 mediates neuronal apoptosis induced by amyloid β-peptide and the membrane lipid peroxidation product 4-hydroxynonenal

The innate immune system senses the invasion of pathogenic microorganisms and tissue injury through Toll-like receptors (TLR), a mechanism thought to be limited to immune cells. We recently found that neurons express several TLRs, and that the levels of TLR2 and TLR4 are increased in neurons in response to energy deprivation. Here we report that TLR4 expression increases in neurons when exposed to amyloid β-peptide (Aβ1–42) or the lipid peroxidation product 4-hydroxynonenal (HNE). Neuronal apoptosis triggered by Aβ and HNE was mediated by jun N-terminal kinase (JNK); neurons from TLR4 mutant mice exhibited reduced JNK and caspase-3 activation and were protected against apoptosis induced by Aβ and HNE. Levels of TLR4 were decreased in inferior parietal cortex tissue specimens from end-stage AD patients compared to aged-matched control subjects, possibly as the result of loss of neurons expressing TLR4. Our findings suggest that TLR4 signaling increases the vulnerability of neurons to Aβ and oxidative stress in AD, and identify TLR4 as a potential therapeutic target for AD.

Physiological and biochemical effects of allelochemical ethyl 2-methyl acetoacetate (EMA) on cyanobacterium Microcystis aeruginosa

The physiological and biochemical effects of an allelochemical ethyl 2-methyl acetoacetate (EMA) isolated from reed ( Phragmites communis) on bloom-forming cyanobacterium, Microcystis aeruginosa, were investigated. EMA significantly inhibited the growth of M. aeruginosa in a concentration-dependent way. The metabolic indices (represented by esterase and total dehydrogenase activities), the cellular redox status (represented by the level of reactive oxygen species (ROS)), and the oxidative damage index (represented by the content of malondialdehyde (MDA), the product of membrane lipid peroxidation) were used to evaluate the physiological and biochemical changes in M. aeruginosa after EMA exposure. Esterase activity in M. aeruginosa did not change ( P>0.05) after 2 h of exposure to EMA, but increased greatly after 24 and 48 h ( P<0.05). EMA exposure (>0.5 mg L −1) resulted in a remarkable loss of total dehydrogenase activity in M. aeruginosa after 4 h ( P<0.01), but an increase after 40 h ( P<0.05). EMA caused a great increase in ROS level of the algal cells. At high EMA concentration (4 mg L −1), the ROS level was remarkably elevated to 1.91 times as much as that in the controls after 2 h. Increases in the ROS level also occurred after 24 and 48 h. The increase in lipid peroxidation of M. aeruginosa was dependent upon EMA concentration and the exposure time. After 40 h of exposure, the MDA content at 4 mg L −1 of EMA reached approximately 3.5 times ( P<0.01) versus the controls. These results suggest that the cellular structure and metabolic activity of M. aeruginosa are influenced by EMA; the increased metabolic activity perhaps reflects the fact that the resistance of cellular response system to the stress from EMA is initiated during EMA exposure, and the oxidative damage induced by EMA via the oxidation of ROS may be an important factor responsible for the inhibition of EMA on the growth of M. aeruginosa.

Effect of Melafen on functional efficiency of mitochondrial membranes from sugar beet taproots

Mitochondria were isolated from sugar beet (Beta vulgaris L) taproots and incubated in the presence of low concentrations of Melafen (2 × 10−9 and 4 × 10−12 M). This treatment of mitochondrial membranes induced an appreciable decrease in microviscosity of superficial lipids in the lipid bilayer and a parallel increase in microviscosity of the deeply immersed lipid regions adjacent to membrane proteins. Melafen had no effect on fluorescence of lipid peroxidation products in membranes of freshly prepared mitochondria but declined this fluorescence to control values in artificially aged mitochondria. Melafen raised the maximum rates for oxidation of NAD-dependent substrates, elevated the efficiency of oxidative phosphorylation, and activated electron transport in the terminal (cytochrome oxidase) step of mitochondrial respiratory chain, which implies the activation of energy metabolism within the cell. The acceleration of electron transport through the terminal step of mitochondrial respiratory chain was apparently accompanied by retardation of lipid peroxidation, which prevented impairment of mitochondrial membranes under stress conditions. A proposal is put forward that some properties of Melafen are favorable for adaptogenesis because its effects on mitochondrial energy metabolism depended on the functional state of mitochondria.

Effects of cinnamic acid on the physiological characteristics of cucumber seedlings under salt stress

Effects of cinnamic acid on the physiological characteristics of cucumber (Shandong Mici) seedlings under salt stress were studied, and the best concentration and treatment time were ascertained. The results showed that cinnamic acid relatively increased the leaf relative water content and the chlorophyll content, decreased plasma membrane permeability, mitigated membrane damage, inhibited the accumulation of malondialdehyde (product of membrane lipid peroxidation), and promoted the activity of membrane protective enzymes such as super oxide dismutase and peroxidase, therefore improving the adaptabilities of cucumber to salt stress. It is concluded that the best treatment time of cinnamic acid is in the two euphylla period, and the best treatment concentration of cinnamic acid is 50 μmol/L.

Effects of Severe Hypocapnia on Expression of Bax and Bcl-2 Proteins, DNA Fragmentation, and Membrane Peroxidation Products in Cerebral Cortical Mitochondria of Newborn Piglets

Background: Hypocapnia occurs in the newborn infant inadvertently or as a therapeutic modality and may result in neuronal and mitochondrial alterations in the newborn brain. Since mitochondria regulate apoptosis, these alterations may initiate a cascade of reactions that lead to apoptotic cell death. Objectives: This study tests the hypothesis that hypocapnia results in increased expression of the pro-apoptotic protein Bax, fragmentation of DNA and membrane lipid peroxidation in cerebral cortical mitochondria (mt) of newborn piglets. Methods: Studies were performed in three groups of anesthetized normoxic newborn piglets: hypocapnic (H, n = 5), ventilated at a PaCO₂ of 11–15 mm Hg; normocapnic (N, n = 5), ventilated at a PaCO₂ of 40 mm Hg; and corrected normocapnic (CN, n = 4), ventilated as H with CO₂ added to maintain normocapnia. Tissue ATP and phosphocreatine levels were determined. Mitochondrial membrane proteins were separated, transblotted and probed with antibodies to Bax and Bcl-2. Bands were detected by enhanced chemiluminescence and analyzed by imaging densitometry. mtDNA was isolated. Cell and mitochondrial membrane lipid peroxidation products were measured spectrofluorometrically. Results: ATP and PCr concentrations were similar in the 3 groups. The ratio of Bax/Bcl-2 increased significantly in H compared to N and CN. mtDNA fragmentation was also significantly greater in H compared to N or CN. Membrane lipid peroxidation was higher in H than in N or CN; and in CN compared to N. Conclusions: The data demonstrate that severe hypocapnia results in increased Bax expression, DNA fragmentation, and membrane lipid peroxidation in mitochondria of cerebral cortical neurons of newborn piglets, and may result in apoptotic cell death.

N-Acetylcysteine and ebselen but not nifedipine protected cerebellar granule neurons against 4-hydroxynonenal-induced neuronal death

4-Hydroxynonenal (HNE), an aldehydic product of membrane lipid peroxidation, has been shown to induce neurotoxicity in various types of neurons. To clarify the mechanisms underlying HNE-induced neurotoxicity, the effects of antioxidants ( N-acetylcysteine (NAC) and ebselen with or without NAC pretreatment) and Ca 2+-related reagents were examined in cerebellar granule neurons. The decreases in neuronal survival and mitochondrial membrane potential induced by HNE were suppressed by pretreatment with NAC at concentrations of 500 and 1000 μM. HNE-induced protein modification and reactive oxygen species generation were also suppressed by pretreatment with NAC at 1000 μM. Although simultaneous application of ebselen (10 μM) did not protect against HNE-induced neurotoxicity, it completely suppressed HNE-induced injury after pretreatment with NAC at 300 μM. HNE increased [Ca 2+] i levels, and this increase was significantly attenuated by simultaneous application of nifedipine (10 μM) or EGTA (1000 μM), but not by MK-801 or CNQX. However, none of these Ca 2+-related reagents was able to prevent HNE-induced neuronal death or mitochondrial injury. These results suggest that pretreatment with a low concentration of NAC dramatically potentiates the neuroprotective activity of ebselen, and that HNE-induced increase in [Ca 2+] i is not involved in HNE-induced neuronal death in cerebellar granule neurons.

Lipid Peroxidation and Serum Antioxidant Enzymes in Patients with Type 2 Diabetes Mellitus

Diabetes mellitus is characterized by fasting hyperglycemia, with both type 1 and type 2 diabetes. Persons are also known to be prone to develop complications related to elevated blood glucose concentrations, including atherosclerosis, retinal damage, cataract, and neuropathy. Hyperglycemia may also result in increased production of the reactive oxygen species within numerous biochemical pathways that have the potential to initiate changes in endothelial function. This article demonstrates the presence of lipid peroxidation products in the red cell membranes of type 2 diabetic patients compared to the normal subjects. These membranes are more susceptible to exogenous oxidative stress than those of normal healthy individuals. Significantly higher activities of antioxidant enzymes, namely, serum peroxidase, superoxide dismutase (SOD), and catalase (CAT) were found in type 2 diabetic patients as compared to control. This study led us to conclude that elevated levels of glucose induce oxidative stress that is ultimately reflected by the increased malondialdehyde (MDA) levels in erythrocyte ghost membranes of diabetic patients. Hyperglycemia also induced an increase in antioxidant enzymes and a relationship seems to exist between diabetic complications and elevated levels of these enzymes. It is suggested that these antioxidant enzymes may be considered as markers for vascular injury.

Dual role of -carotene in combination with cigarette smoke aqueous extract on the formation of mutagenic lipid peroxidation products in lung membranes: dependence on pO2

Results from some intervention trials indicated that supplemental beta-carotene enhanced lung cancer incidence and mortality in chronic smokers. The aim of this study was to verify the hypothesis that high concentrations of the carotenoid, under the pO2 present in lung (100-150 mmHg), may exert deleterious effects through a prooxidant mechanism. To test this hypothesis, we examined the interactions of beta-carotene and cigarette smoke condensate (tar) on the formation of lipid peroxidation products in rat lung microsomal membranes enriched in vitro with varying beta-carotene concentrations (from 1 to 10 nmol/mg prot) and then incubated with tar (6-25 microg/ml) under different pO2. As markers of lipid peroxidation, we evaluated the levels of conjugated dienes and malondialdehyde, possessing mutagenic and pro-carcinogenic activity. The exposure of microsomal membranes to tar induced a dose-dependent enhancement of lipid peroxidation, which progressively increased as a function of pO2. Under a low pO2 (15 mmHg), beta-carotene acted clearly as an antioxidant, inhibiting tar-induced lipid peroxidation. However, the carotenoid progressively lost its antioxidant efficiency by increasing pO2 (50-100 mmHg) and acted as a prooxidant at pO2 ranging from 100 to 760 mmHg in a dose-dependent manner. Consistent with this finding, the addition of alpha-tocopherol (25 microM) prevented the prooxidant effects of the carotenoid. beta-Carotene auto-oxidation, measured as formation of 5,6-epoxy-beta,beta-carotene, was faster at high than at low pO2 and the carotenoid was more rapidly consumed in the presence of tar. These data point out that the carotenoid may enhance cigarette smoke-induced oxidative stress and exert potential deleterious effects at the pO2 normally present in lung tissue.

The Relationship Between Senescence and Ca 2+-ATPase Activity of Microsomal Membrane and Lipid Peroxidation in Harvested Peach Fruit

Peach fruit easily soften and have a short storage time at normal temperature. In this study, peach fruit ( Prunus persica sieb et Zucc cv. Yingqing) were picked and stored at 25 and 4°C to investigate the senescence in correlation with Ca 2+-ATPase activity of microsomal membrane and lipid peroxidation during ripening and senescence. In comparison with that stored at 25°C, the fruit stored at 4°C exhibited a higher flesh firmness, lower respiration rate, and generated the late bigger peak value of Ca 2+-ATPase activity as well as maintained the higher activity of the enzyme. Meanwhile, the lower levels of super oxygen radical (O 2 ▪) production and content of malondialdehyde (MDA), a product of membrane lipid peroxidation were observed. Sodium orthovanadate (SO) and erythrosin B (EB), as Ca 2+-ATPase inhibitors, could stimulate the respiration rate. The results suggested that the slower senescence rate of peach fruit was closely related to the higher peak value and longer duration of Ca 2+-ATPase activity in microsomal membrane, with the slighter membrane lipid peroxidation and lower ▪ production rate.

Antioxidative enzyme and glutathione S-transferase activities in diabetic rats exposed to long-term ASA treatment

Low-dose acetylsalicylic acid (ASA) treatment is a standard therapeutic approach in diabetes mellitus for prevention of long-term vascular complications. The aim of the present work was to investigate the effect of long-term ASA administration in experimental diabetes on activities of some liver enzymes: glutathione peroxidase (GSHPx), catalase, glucose-6-phosphate dehydrogenase (G6PDH) and glutathione S-transferase (GST). Blood glucose, glycated hemoglobin, as well as plasma ALT and AST activities increased in rats with streptozotocin-induced experimental diabetes. The long-term hyperglycemia resulted in decreased activities of GSHPx (by 26%), catalase (by 34%), GST (by 38%) and G6PDH (by 27%) in diabetic animals. We did not observe increased accumulation of membrane lipid peroxidation products or altered levels of reduced glutathione in livers. The linear correlation between blood glucose and glycated hemoglobin in diabetic animals was distorted upon ASA treatment, which was likely due to a chemical competition between nonenzymatic protein glycosylation and protein acetylation. The long-term ASA administration partially reversed the decrease in GSHPx activity, but did not influence the activities of catalase and GST in diabetic rats. Otherwise, some decrease in these parameters was noted in ASA-treated nondiabetic animals. Increased ASA-induced G6PDH activity was recorded in both diabetic and nondiabetic rats. While both glycation due to diabetic hyperglycemia and ASA-mediated acetylation had very similar effects on the activities of all studied enzymes but G6PDH, we conclude that non-enzymatic modification by either glucose or ASA may be a common mechanism of the observed convergence.

N-acetylcysteine selectively protects cerebellar granule cells from 4-hydroxynonenal-induced cell death

4-Hydroxynonenal (HNE), an aldehydic product of membrane lipid peroxidation, has been shown to induce neurotoxicity accompanied by multiple events. To clarify mechanisms of neuroprotective compounds on HNE-induced toxicity, the protective effects of N-acetylcysteine (NAC), α-tocopherol (TOC), ebselen and S-allyl- l-cysteine (SAC) were compared in cerebellar granule neurons. The decrease in MTT reduction induced by HNE was significantly suppressed by pretreatment of the neurons with 1000 μM NAC or 10 and 100 μM TOC; however, lactate dehydrogenase (LDH) release and propidium iodide (PI) fluorescence studies revealed that neuronal death was suppressed by NAC but not by TOC. Treatment of these neurons with HNE resulted in a drastic reduction of mitochondrial membrane potential, and this reduction was also prevented by NAC but not by TOC. Ebselen and SAC, a garlic compound, were unable to protect these neurons against HNE-induced toxicity. Pretreatment with NAC also prevented HNE-induced depletion of intracellular glutathione (GSH) levels in these neurons. These results suggest that NAC, but not other antioxidants such as TOC, SAC and ebselen, exerts significant protective effects against HNE-induced neuronal death in cerebellar granule neurons, and that this neuroprotective effect is due, at least in part, to preservation of mitochondrial membrane potential and intracellular GSH levels.

Photosynthesis and antioxidant enzyme activity in breadfruit, jackfruit and mangosteen in Southern Yunnan, China

SummaryThe Xishuangbanna Prefecture (21°09'-22°36' N; 99°58'-101°50' E) in southern Yunnan is one of the major growing areas for tropical crops in China. Daily temperature in Winter is about 8°C lower that in Summer.The effects of season on photosynthesis and antioxidant enzyme activities were studied in the tropical fruit tree species Artocarpus altilis (breadfruit), A. heterophyllus (jackfruit) and Garcinia mangostana (mangosteen), growing in an open site. In August 2002 and January 2003, maximum net CO2 assimilation was 17.1 ± 0.3 µmoles m–2 s–1 (mean ± SE) and 10.7 ± 0.5 in breadfruit; 11.7 ± 0.2 µmoles m–2 s–1 and 10.9 ± 0.6 in jackfruit; and 8.6 ± 0.1 µmoles m–2 s–1 and 6.3 ± 0.4 in mangosteen, respectively. Concentrations of chlorophyll were lower in mangosteen and breadfruit in January than in August, while in January, photo-inhibition was evident in mangosteen and breadfruit by changes in leaf chlorophyll fluorescence. Concentrations of malondialdehyde (a product of membrane lipid peroxidation), carotenoid to chlorophyll ratios, and the activities of the antioxidant enzymes superoxide dismutase, catalase and peroxidase were higher in January than in August, in all species, especially the antioxidant enzyme activities in jackfruit. Moreover, in both August and January, mangosteen suffered severe mid-day photo-inhibition. These results indicate that jackfruit is chilling tolerant, breadfruit is chilling sensitive, and mangosteen is chilling and high-light intensity sensitive. Breadfruit and mangosteen do not appear to be suitable crops to grow outdoors in southern Yunnan, China.

4-Hydroxynonenal signalling to apoptosis in isolated rat hepatocytes: The role of PKC-δ

4-Hydroxynonenal, a significant aldehyde end product of membrane lipid peroxidation with numerous biochemical activities, has consistently been detected in various human diseases. Concentrations actually detectable in vivo (0.1–5 μM) have been shown to up-regulate different genes and modulate various enzyme activities. In connection with the latter aspect, we show here that, in isolated rat hepatocytes, 1 μM 4-hydroxynonenal selectively activates protein kinase C-δ, involved in apoptosis of many cell types; it also induces very early activation of Jun N-terminal kinase, in parallel increasing activator protein-1 DNA-binding activity in a time-dependent manner and triggering apoptosis after only 120 min treatment. These phenomena are likely protein kinase C-δ-dependent, being significantly reduced or annulled by cell co-treatment with rottlerin, a selective inhibitor of protein kinase C-δ. We suggest that 4-hydroxynonenal may induce apoptosis through activation of protein kinase C-δ and of Jun N-terminal kinase, and consequent up-regulation of activator protein-1 DNA binding.

Oxidative Processes Induced by tert-Butyl Hydroperoxide in Human Red Blood Cells: Chemiluminescence Studies

The erythrocyte is a good model for investigation of the mechanisms of cell damage induced by oxidizing agents. Oxidative damage to cell components and cellular metabolism results in impaired rheological properties of circulating red blood cells and is involved in the development of some pathologies. The aim of the present study was to elucidate further the oxidative processes induced by tert-butyl hydroperoxide (tBOOH) in erythrocytes, identify cellular targets damaged by the oxidant, as well as estimate the energy and stoichiometry of the reactions that occur. The generation of free radicals in the cell was registered using the chemiluminescence technique. The products of oxyhemoglobin (oxyHb) oxidation, changes in intracellular glutathione (GSH) pool, and accumulation of the stable products of membrane lipid peroxidation were concurrently measured. The oxidative processes induced by tBOOH in red blood cells can be described as follows: 1) rapid GSH oxidation (30-60 sec) by glutathione peroxidase; 2) formation of radicals in the reaction between tBOOH and cellular Hb, which are then immediately consumed in lipid peroxidation reactions; 3) generation of chemiluminescence by the radicals formed. Several stages of the oxidative processes can be revealed. The order of the chemiluminescence reaction (n) with respect to oxidant was estimated to be equal to 2.5 at oxidant concentrations less than 0.5 mM and equal to 1.0 at higher oxidant concentrations. The order of the reaction of membrane lipid peroxidation was found to be n = 2.2 at 0.25-0.6 mM tBOOH and n = 0.5 at higher oxidant concentrations. The apparent activation energy of membrane lipid peroxidation was 55.8 +/- 6.4 kJ/mol, and that of oxyHb oxidation was 108 +/- 16 kJ/mol. It is shown that the interaction of tBOOH and HOCl in erythrocytes is accompanied by changes in both the total number of radicals generated in the cell and the time corresponding to the maximal rate of radical generation.

Effects of heat acclimation pretreatment on changes of membrane lipid peroxidation, antioxidant metabolites, and ultrastructure of chloroplasts in two cool-season turfgrass species under heat stress

The membrane lipid peroxidation, antioxidant metabolites, as well as ultrastructure of chloroplasts of leaves were investigated in two cool-season turfgrass species, perennial ryegrass (heat sensitive) and tall fescue (moderate), exposed to three heat stress levels (38, 42, 46 °C) for 14 h, respectively, with a heat acclimation pretreatment at 30 °C for 3 days in a growth chamber. Relative water content (RWC), cell membrane thermostability, malondialdehyde (MDA) content, accumulation of hydrogen peroxide (H 2O 2) and superoxide (O 2 −), ascorbate (AsA) and glutathione (GSH) contents were measured in leaves. RWC decreased with increase in heat stress levels in tall fescue and perennial ryegrass leaves. However, leaves with heat acclimation pretreatment kept lower decrease in RWC than those without heat acclimation pretreatment at three heat stress levels. Under heat stresses, leaves heat-acclimated pretreatment in two turfgrass species maintained higher membrane thermostability and lower membrane lipid peroxidation product (MDA) than those in no heat-acclimated leaves; however, perennial ryegrass leaves showed greater membrane injury than tall fescue leaves regardless of heat acclimation pretreatment, especially at 46 °C. Significant accumulation of H 2O 2 and O 2 − was observed in two turfgrass species leaves regardless of heat-acclimated pretreatment at all stress levels; however, their degree of accumulation kept lower level in heat-acclimated leaves than in no heat-acclimated leaves. AsA and GSH are two important metabolites in antioxidant system in plants. Our results showed the contents of AsA and GSH in heat-acclimated leaves were higher than those in control at same heat stress level though the contents of AsA and GSH showed the trend of significant decrease with increase in heat stress levels. After heat acclimation pretreatment, ultrastructure of chloroplasts had lower damage in two turfgrass species leaves under heat stress than those without heat acclimation pretreatment, which may contribute to the decrease in membrane lipid peroxidation, increase in AsA and GSH contents at same heat stress level. However, it was insufficient to protect the chloroplast from damage with increase in heat stress level, even if with high AsA and GSH contents to remove reactive oxygen species (ROS).

Oxidatively Modified GST and MRP1 in Alzheimer?s Disease Brain: Implications for Accumulation of Reactive Lipid Peroxidation Products

Alzheimer disease (AD) is a neurodegenerative disorder characterized pathologically by intracellular inclusions including neurofibrillary tangles (NFT) and senile plaques. Several lines of evidence implicate oxidative stress with the progression of AD. 4-hydroxy-2-trans-nonenal (HNE), an aldehydic product of membrane lipid peroxidation, is increased in AD brain. The alpha class of glutathione S-transferase (GST) can detoxify HNE and plays an important role in cellular protection against oxidative stress. The export of the glutathione conjugate of HNE is required to fully potentiate the GST-mediated protection. The multidrug resistance protein-1 (MRP1) and GST proteins may act in synergy to confer cellular protection. In the present study, we studied oxidative modification of GST and MRP1 in AD brain by immunoprecipitation of GST and MRP1 proteins followed by Western blot analysis using anti-HNE antibody. The results suggested that HNE is covalently bound to GST and MRP1 proteins in excess in AD brain. Collectively, the data suggest that HNE may be an important mediator of oxidative stress-induced impairment of this detoxifying system and may thereby play a role in promoting neuronal cell death. The results from this study also imply that augmenting endogenous oxidative defense capacity through dietary or pharmacological intake of antioxidants may slow down the progression of neurodegenerative processes in AD.