Brain mitochondrial dysfunction and oxidative damage in Parkinson’s disease

Complex factors contribute to the appearance of Parkinson’s disease (PD), but with a constant mitochondrial involvement. There are two interdependent conditions in PD: brain mitochondrial dysfunction and brain mitochondrial oxidative damage. Mitochondrial dysfunction and reduced complex I activity are recognized in substantia nigra and in frontal cortex in PD patients. The molecular mechanism involved in the inactivation of complex I is likely accounted by the sum of ONOO⁻ mediated reactions, reactions with free radical intermediates of the lipid peroxidation process and amine-aldehyde adduction reactions. The inhibitory effects on complex I lead synergistically to denaturation of the protein structure and to further increases of O₂⁻ and ONOO⁻ production at the vicinity of complex I. An adaptive response in PD patients has been described with increases in mtNOS activity, mitochondrial mass and mitochondrial biogenesis. Mitochondrial dysfunction in the human frontal cortex is to be considered a factor contributing to impaired cognition in PD.     

Functional argument for the existence of an avian nitric oxide synthase in muscle mitochondria: effect of cold acclimation

We report the first evidence of a mitochondrial NO synthase (mtNOS) in bird skeletal muscle. In vitro, mtNOS activity stimulated by l-arginine reduced intermyofibrillar mitochondrial oxygen uptake and ATP synthesis rates, stimulated endogenous H₂O₂ generation, but had no effect on oxidative phosphorylation efficiency. Arginine-induced effects were fully reversed by l-NAME, a known NOS inhibitor. When ducklings were cold exposed for 4 weeks, muscle mitochondria displayed an increased state 3 respiration, a reduced H₂O₂ generation but no significant alteration in mtNOS activity. We conclude that mtNOS is expressed in avian skeletal muscle.     

Impact of oxidative stress on <Emphasis Type="Italic">Acanthamoeba castellanii</Emphasis> mitochondrial bioenergetics depends on cell growth stage

Addition of a moderate (1.4 mM) concentration of H₂O₂ to protozoon Acanthamoeba castellanii cell cultures at different growth phases caused a different response to oxidative stress. H₂O₂ treatment of exponentially growing cells significantly delayed their growth; however, in mitochondria isolated from these cells, no damage to their bioenergetic function was observed. In contrast, addition of H₂O₂ to A. castellanii cells approaching the stationary phase did not influence their growth and viability while seriously affecting mitochondrial bioenergetic function. Although mitochondrial integrity was maintained, oxidative damage was revealed in the reduction of cytochrome pathway activity, uncoupling protein activity, and the efficiency of oxidative phosphorylation as well as the membrane potential and the endogenous ubiquinone reduction level of the resting state. An increase in the alternative oxidase protein level and activity as well as an increase in the membranous ubiquinone content were observed in mitochondria isolated from late H₂O₂-treated cells. For the first time, the regulation of ubiquinone content in the inner mitochondrial membrane is shown to play a role in the response to oxidative stress. A physiological role for the higher activity of the alternative oxidase in response to oxidative stress in unicellular organisms, such as amoeba A. castellanii, is discussed.     

Moderate intermittent hypoxia/hyperoxia: implication for correction of mitochondrial dysfunction

The purpose of this study was to appreciate the acute hypoxia-induced mitochondrial oxidative damage development and the role of adaptation to hypoxia/hyperoxia (H/H) in correction of mitochondrial dysfunction. It was demonstrated that long-term sessions of moderate H/H [5 cycles of 5 min hypoxia (10% O₂ in N₂) alternated with 5 min hyperoxia (30% O₂ in N₂) daily for two weeks]_attenuated basal and Fe²⁺/ascorbate-induced lipid peroxidation (LPO) as well as production of carbonyl proteins and H₂O₂ in liver mitochondria of rats exposed to acute severe hypoxia (7% O₂ in N₂, 60 min) in comparison with untreated animals. It was shown that H/H increases the activity of glutathione peroxidase (GPx), reduces hyperactivation of Mn-SOD, and decreases Cu,Zn-SOD activity as compared with untreated rats. It has been suggested that the induction of Mn-SOD protein expression and the coordinated action of Mn-SOD and GPx could be the mechanisms underlying protective effects of H/H, which promote the correction of the acute hypoxia-induced mitochondrial dysfunction. The increase in Mn-SOD protein synthesis without changes in Mn-SOD mRNA level under H/H pretreatment indicates that the Mn-SOD activity is most likely dependent on its posttranslational modification or on the redox state of liver mitochondria.     

Complex I syndrome in myocardial stunning and the effect of adenosine

Isolated rabbit hearts were exposed to ischemia (I; 15 min) and reperfusion (R; 5-30 min) in a model of stunned myocardium. I/R decreased left-ventricle O₂ consumption (46%) and malate-glutamate-supported mitochondrial state 3 respiration (32%). Activity of complex I was 28% lower after I/R. The pattern observed for the decline in complex I activity was also observed for the reduction in mitochondrial nitric oxide synthase (mtNOS) biochemical (28%) and functional (50%) activities, in accordance with the reported physical and functional interactions between complex I and mtNOS. Malate-glutamate-supported state 4 H₂O₂ production was increased by 78% after I/R. Rabbit heart Mn-SOD concentration in the mitochondrial matrix (7.4 ± 0.7 μM) was not modified by I/R. Mitochondrial phospholipid oxidation products were increased by 42%, whereas protein oxidation was only slightly increased. I/R produced a marked (70%) enhancement in tyrosine nitration of the mitochondrial proteins. Adenosine attenuated postischemic ventricular dysfunction and protected the heart from the declines in O₂ consumption and in complex I and mtNOS activities and from the enhancement of mitochondrial phospholipid oxidation. Rabbit myocardial stunning is associated with a condition of dysfunctional mitochondria named “complex I syndrome.” The beneficial effect of adenosine could be attributed to a better regulation of intracellular cardiomyocyte Ca²⁺ concentration.     

Endotoxemia impairs heart mitochondrial function by decreasing electron transfer, ATP synthesis and ATP content without affecting membrane potential

Acute endotoxemia (LPS, 10 mg/kg ip, Sprague Dawley rats, 45 days old, 180 g) decreased the O₂ consumption of rat heart (1 mm³ tissue cubes) by 33% (from 4.69 to 3.11 μmol O₂/min. g tissue). Mitochondrial O₂ consumption and complex I activity were also decreased by 27% and 29%, respectively. Impaired respiration was associated to decreased ATP synthesis (from 417 to 168 nmol/min. mg protein) and ATP content (from 5.40 to 4.18 nmol ATP/mg protein), without affecting mitochondrial membrane potential. This scenario is accompanied by an increased production of O₂^●− and H₂O₂ due to complex I inhibition. The increased NO production, as shown by 38% increased mtNOS biochemical activity and 31% increased mtNOS functional activity, is expected to fuel an increased ONOO⁻ generation that is considered relevant in terms of the biochemical mechanism. Heart mitochondrial bioenergetic dysfunction with decreased O₂ uptake, ATP production and contents may indicate that preservation of mitochondrial function will prevent heart failure in endotoxemia.     

Effects of intermittent hypoxia different regimes on mitochondrial lipid peroxidation and glutathione-redox balance in stressed rats

The purpose of this study was to compare the influence of two regimes of intermittent hypoxia (IH) [repetitive 5 cycles of 5 min hypoxia (7% O₂ or 12% O₂ in N₂) followed by 15 min normoxia, daily for three weeks] on oxidative stress protective systems in liver mitochondria. To estimate the effectiveness of hypoxia adaptation at the early and late preconditioning period, we exposed rats to acute 6-h immobilization at the 1^st and 45^th days after cessation of IH. We showed that severity of hypoxic episodes during IH might initiate different adaptive programs. Moderate hypoxia during IH prevents mitochondrial glutathione pool depletion induced by immobilization stress, maintains GSH-redox cycle via activation of glutathione peroxidase, glutathione-S-transferase, glutathione reductase, NADP⁺-dependent isocitrate dehydrogenase, and increases Mn-SOD activity. Such regimen of hypoxic preconditioning caused the decrease of mitochondrial superoxide anion generation as well as of basal and stimulated in vitro lipid peroxidation and this protective effect remained for 45 days under renormoxic conditions. Hypoxic adaptation in a more severe regimen exerted beneficial effects on the mitochondrial antioxidant defense system only at its later phase.     

Effect of Long-Term Normobaric Hyperoxia on Oxidative Stress in Mitochondria of the Guinea Pig Brain

Normobaric hyperoxia (NBO) is applied for treatment of various clinical conditions related to hypoxia, but it can potentially also induce generation of reactive oxygen species, causing cellular damage. In this study, we examined the effects of 60 h NBO treatment on lipid and protein oxidative damage and activity of superoxide dismutase (Mn-SOD) in brain mitochondria of guinea pigs. Despite significant stimulation of Mn-SOD expression and activity the NBO treatment resulted in accumulation of markers of oxidative lesions, including lipid peroxidation (conjugated dienes, thiobarbituric acid reactive substances) and protein modification (bityrosines, adducts with lipid peroxidation products, oxidized thiols). When inhaled O₂ was enriched with oxygen cation, O₂^•+, the Mn-SOD expression and activity were stimulated to similar extend, but lipid peroxidation and protein oxidation were prevented. These results suggest that long-term NBO treatment causes oxidative stress, but enrichment of inhaled oxygen by oxygen cation can protect the brain again adverse effects of hyperoxia.     

Mitochondrial nitric oxide metabolism in rat muscle during endotoxemia

In this study, heart and diaphragm mitochondria produced 0.69 and 0.77 nmol nitric oxide (NO)/min mg protein, rates that account for 67 and 24% of maximal cellular NO production, respectively. Endotoxemia and septic shock occur with an exacerbated inflammatory response that damages tissue mitochondria. Skeletal muscle seems to be one of the main target organs in septic shock, showing an increased NO production and early oxidative stress. The kinetic properties of mitochondrial nitric oxide synthase (mtNOS) of heart and diaphragm were determined. For diaphragm, the KM values for O2 and L-Arg were 4.6 and 37 microM and for heart were 3.3 and 36 microM. The optimal pH for mtNOS activity was 6.5 for diaphragm and 7.0 for heart. A marked increase in mtNOS activity was observed in endotoxemic rats, 90% in diaphragm and 30% in heart. Diaphragm and heart mitochondrial O2*- and H2O2 production were 2- to 3-fold increased during endotoxemia and Mn-SOD activity showed a 2-fold increase in treated animals, whereas catalase activity was unchanged. One of the current hypotheses for the molecular mechanisms underlying the complex condition of septic shock is that the enhanced NO production by mtNOS leads to excessive peroxynitrite production and protein nitration in the mitochondrial matrix, causing mitochondrial dysfunction and contractile failure.     

Oxidative Damage and Mitochondrial Injuries Are Induced by Various Irrigation Pressures in Rabbit Models of Mild and Severe Hydronephrosis

Objective

We aimed to study whether tolerance to irrigation pressure could be modified by evaluating the oxidative damage of obstructed kidneys based on rabbit models experiencing different degrees of hydronephrosis.

Methods

A total of 66 rabbits were randomly divided into two experimental groups and a control group. In the experimental groups, the rabbits underwent a surgical procedure inducing mild (group M, n=24) or severe (group S, n=24) hydronephrosis. In each experimental group, the rabbits were then randomly divided into 4 subgroups (M0-M3 and S0-S3) consisting of 6 rabbits each. Group 0 received no perfusion. Groups 1 through 3 were perfused with 20, 60 and 100 mmHg fluid, respectively. For the control group, after a sham operation was performed, the rabbits were divided into 4 subgroups and were perfused with fluid at 0, 20, 60 or 100 mmHg of pressure. Kidney injuries was evaluated by neutrophil gelatinase associated lipocalin (NGAL). Oxidative damage was assessed by analyzing superoxide dismutase (Mn-SOD) activity, malondialdehyde (MDA) levels, glutathione reductase (GR), catalase (CAT) and peroxide (H₂O₂) levels, mitochondrial injuries was assessed by mitochondrial membrane potential (MMP), the mitochondrial ultrastructure and tubular cell apoptosis.

Results

In the experimental groups, all results were similar for groups 0 and 1. In group 2, abnormalities were observed in the S group only, and the kidneys of rabbits in group 3 suffered oxidative damage and mitochondrial injuries with increased NGAL, decreased Mn-SOD, GR and CAT,increased MDA and H₂O₂, lower levels of MMP, mitochondrial vacuolization and an increased apoptotic index.

Conclusion

In rabbits, severely obstructed kidneys were more susceptible to oxidative damage and mitochondrial injury than mildly obstructed kidneys when subjected to higher degrees of kidney perfusion pressure.     

Moderate O3/O2 therapy enhances enzymatic and non-enzymatic antioxidant in brain and cochlear that protects noise-induced hearing loss

Mitochondrial damage and oxidative stress are known to contribute to the pathogenesis of noise-induced hearing loss (NIHL). In this study, we examined the protective effect of O₂/O₃ mixture (ozone/oxygen) therapy against mitochondrial induced damage and oxidative stress by noise exposure in rat brain and cochlear. For this purpose, rats were divided into four groups: 1 – control group; 2 – noise-exposed group (100?dB); 3 – noise?+?O₂/O₃, and 4 – O₂/O₃ (30 µg/ml). After 14 d, animals were anesthetised. Rat brain and cochlear tissue were removed for evaluation of the histopathological damages, oxidative stress, and mitochondrial dysfunction in both tissues. Our findings indicated that noise caused pathological damage, oxidative stress, and mitochondrial dysfunction in rat brain and cochlear. Also, daily administration of an O₂/O₃ therapy (30 µg/ml intravenous) efficiently increased enzymatic and non-enzymatic antioxidant in brain and cochlear that this action led to inhibition of pathological damages, oxidative stress, reactive oxygen species formation, mitochondrial membrane potential (MMP) collapse, mitochondrial swelling, and cytochrome c release resulting from noise. These findings suggest that the moderate O₂/O₃ therapy enhances the capacity of enzymatic and non-enzymatic antioxidant in brain and cochlear that protects against NIHL.     

Scavenger Enzyme Activities in Subcellular Fractions of White Clover (Trifolium repens L.) under PEG-induced Water Stress

Scavenger enzyme activities in subcellular fractions under polyethylene glycol (PEG)-induced water stress in white clover (Trifolium repens L.) were studied. Water stress decreased ascorbic acid (AA) content and catalase (CAT) activity and increased the contents of hydrogen peroxide (H₂O₂), thiobarbituric acid reactive substances (TBARS) (measure of lipid peroxidation), and activities of superoxide dismutase (SOD), its various isozymes, ascorbate peroxidase (APOX), and glutathione reductase (GR) in cellular cytosol, chloroplasts, mitochondria, and peroxisomes of Trifolium repens leaves. In both the PEG-treated plants and the control, chloroplastic fractions showed the highest total SOD, APOX, and GR activities, followed by mitochondrial fractions in the case of total SOD and GR activities, whereas cytosolic fractions had the second greatest APOX activity. However, CAT activity was the highest in peroxisomes, followed by the cytosol, mitochondria, and chloroplasts in decreasing order. Although Mn-SOD activity was highest in mitochondrial fractions, residual activity was also observed in cytosolic fractions. Cu/Zn-SOD and Fe-SOD were observed in all subcellular fractions; however, the activities were the highest in chloroplastic fractions for both isoforms. Total Cu/Zn-SOD activity, the sum of activities observed in all fractions, was higher than other SOD isoforms. These results suggest that cytosolic and chloroplastic APOX, chloroplastic and mitochondrial GR, mitochondrial Mn-SOD, cytosolic and chloroplastic Cu/Zn-SOD, and chloroplastic Fe-SOD are the major scavenger enzymes, whereas cellular CAT may play a minor role in scavenging of O₂⁻ and H₂O₂ produced under PEG-induced water stress in Trifolium repens.     

Molecular role of catalase on oxidative stress-induced Ca2+ signaling and TRP cation channel activation in nervous system

Background: Catalase catalyzes the reduction of H₂O₂ to water and it can also remove organic hydroperoxides. Nervous system in body is especially sensitive to free radical damage due to rich content of easily oxidizible fatty acids and relatively low content of antioxidants including catalase. Recent studies indicate that reactive oxygen species actually target active channel function, in particular TRP channels. I review the effects of catalase on Ca²⁺ signaling and on TRP channel activation in neuroglial cells such as microglia and substantia nigra.

Materials: Review of the relevant literature and results from recent our basic studies, as well as critical analyses of published systematic reviews were obtained from the pubmed and the Science Citation Index.

Results: It was observed that oxidative stress-induced activations of TRPM2, TRPC3, TRPC5 and TRPV1 cation channels in neuronal cells are modulated by catalase, suggesting antioxidant-dependent activation/inhibition of the channels. I provide also, a general overview of the most important oxidative stress-associated changes in neuronal mitochondrial Ca²⁺ homeostasis due to oxidative stress-induced channel neuropathies. Catalase incubation induces protective effects on rat brain mitochondrial function and neuronal survival. A decrease in catalase activity through oxidative stress may have an important role in etiology of Parkinson’s disease and sensory pain.

Conclusion: The TRP channels can be activated by oxidative stress products, opening of nonspecific cation channels would result in Ca²⁺ influx, and then elevation of cytoplasmic free Ca²⁺ could stimulate mitochondrial Ca²⁺ uptake. Catalase modulates oxidative stress-induced Ca²⁺ influx and some TRP channels activity in neuronal cells.     

Diabetes impairs heart mitochondrial function without changes in resting cardiac performance

Diabetes is a chronic disease associated to a cardiac contractile dysfunction that is not attributable to underlying coronary artery disease or hypertension, and could be consequence of a progressive deterioration of mitochondrial function. We hypothesized that impaired mitochondrial function precedes Diabetic Cardiomyopathy. Thus, the aim of this work was to study the cardiac performance and heart mitochondrial function of diabetic rats, using an experimental model of type I Diabetes. Rats were sacrificed after 28 days of Streptozotocin injection (STZ, 60 mg kg⁻¹, ip.). Heart O₂ consumption was declined, mainly due to the impairment of mitochondrial O₂ uptake. The mitochondrial dysfunction observed in diabetic animals included the reduction of state 3 respiration (22%), the decline of ADP/O ratio (∼15%) and the decrease of the respiratory complexes activities (22–26%). An enhancement in mitochondrial H₂O₂ (127%) and NO (23%) production rates and in tyrosine nitration (58%) were observed in heart of diabetic rats, with a decrease in Mn-SOD activity (∼50%). Moreover, a decrease in contractile response (38%), inotropic (37%) and lusitropic (58%) reserves were observed in diabetic rats only after a β‐adrenergic stimulus. Therefore, in conditions of sustained hyperglycemia, heart mitochondrial O₂ consumption and oxidative phosphorylation efficiency are decreased, and H₂O₂ and NO productions are increased, leading to a cardiac compromise against a work overload. This mitochondrial impairment was detected in the absence of heart hypertrophy and of resting cardiac performance changes, suggesting that mitochondrial dysfunction could precede the onset of diabetic cardiac failure, being H₂O₂, NO and ATP the molecules probably involved in mitochondrion-cytosol signalling.     

Evaluation of Markers of Oxidative Stress,Antioxidant Function and Astrocytic Proliferation in the Striatum and Frontal Cortex of Parkinson’s Disease Brains

Dopaminergic neurons die in Parkinson’s disease (PD) due to oxidative stress and mitochondrial dysfunction in the substantia nigra (SN). We evaluated if oxidative stress occurs in other brain regions like the caudate nucleus (CD), putamen (Put) and frontal cortex (FC) in human postmortem PD brains (n = 6). While protein oxidation was elevated only in CD (P < 0.05), lipid peroxidation was increased only in FC (P < 0.05) and protein nitration was unchanged in PD compared to controls. Interestingly, mitochondrial complex I (CI) activity was unaffected in PD compared to controls. There was a 3–5 fold increase in the total glutathione (GSH) levels in the three regions (P < 0.01 in FC and CD; P < 0.05 in Put) but activities of antioxidant enzymes catalase, superoxide dismutase, glutathione reductase and glutathione-s-tranferase were not increased. Total GSH levels were elevated in these areas because of decreased activity of gamma glutamyl transpeptidase (γ-GT) (P < 0.05) activity suggesting a decreased breakdown of GSH. There was an increase in expression of glial fibrillary acidic protein (GFAP) (P < 0.001 in FC; P < 0.05 in CD) and glutathione peroxidase (P < 0.05 in CD and Put) activity due to proliferation of astrocytes. We suggest that increased GSH and astrocytic proliferation protects non-SN brain regions from oxidative and mitochondrial damage in PD.     

Lrrk2 interaction with α-synuclein in diffuse Lewy body disease

Mutations of the leucine-rich repeat kinase 2 (LRRK2) gene are the leading cause of genetically inherited Parkinson’s disease (PD) and its more severe variant diffuse Lewy body disease (DLB). Pathological mutations in Lrrk2 are autosomal dominant, suggesting a gain of function. Mutations in α-synuclein also produce autosomal dominant disease. Here we report an interaction between Lrrk2 and α-synuclein in a series of diffuse Lewy body (DLB) cases and in an oxidative stress cell based assay. All five cases of DLB, but none of five controls, showed co-immunoprecipitation of Lrrk2 and α-synuclein in soluble brain extracts. Colocalization was also found in pathological deposits in DLB postmortem brains by double immunostaining. In HEK cells transfected simultaneously with plasmids expressing Lrrk2 and α-synuclein, co-immunoprecipitation of Lrrk2 and α-synuclein was detected when they were exposed to oxidative stress by H₂O₂. Taken together, these results suggest the possibility that in PD and related synucleinopathies, oxidative stress upregulates α-syn and Lrrk2 expression, paving the way for pathological interactions. New therapeutic approaches to PD and the synucleinopathies may result from limiting the interaction between Lrrk2 and α-synuclein.     

Effect of T3 on metabolic response and oxidative stress in skeletal muscle from sedentary and trained rats

We investigated whether swim training modifies the effect of T₃-induced hyperthyroidism on metabolism and oxidative damage in rat muscle. Respiratory capacities, oxidative damage, levels of antioxidants, and susceptibility to oxidative challenge of homogenates were determined. Mitochondrial respiratory capacities, H₂O₂ release rates, and oxidative damage were also evaluated. T₃-treated rats exhibited increases in muscle respiratory capacity, which were associated with enhancements in mitochondrial respiratory capacity and tissue mitochondrial protein content in sedentary and trained animals, respectively. Hormonal treatment induced muscle oxidative damage and GSH depletion. Both effects were reduced by training, which also attenuated tissue susceptibility to oxidative challenge. The changes in single antioxidant levels were slightly related to oxidative damage extent, but the examination of parameters affecting the susceptibility to oxidants indicated that training was associated with greater effectiveness of the muscle antioxidant system. Training also attenuated T₃-induced increases in H₂O₂ production and, therefore, oxidative damage of mitochondria by lowering their content of autoxidizable electron carriers. The above results suggest that moderate training is able to reduce hyperthyroid state-linked tissue oxidative damage, increasing antioxidant protection and decreasing the ROS flow from the mitochondria to the cytoplasmic compartment.     

Alteration in Glutathione Content and Associated Enzyme Activities in the Synaptic Terminals but not in the Non-synaptic Mitochondria from the Frontal Cortex of Parkinson’s Disease Brains

Altered redox dynamics contribute to physiological aging and Parkinson’s disease (PD). This is reflected in the substantia nigra (SN) of PD patients as lowered antioxidant levels and elevated oxidative damage. Contrary to this observation, we previously reported that non-SN regions such as caudate nucleus and frontal cortex (FC) exhibited elevated antioxidants and lowered mitochondrial and oxidative damage indicating constitutive protective mechanisms in PD brains. To investigate whether the sub-cellular distribution of antioxidants could contribute to these protective effects, we examined the distribution of antioxidant/oxidant markers in the neuropil fractions [synaptosomes, non-synaptic mitochondria and cytosol] of FC from PD (n = 9) and controls (n = 8). In the control FC, all the antioxidant activities [Superoxide dismutase (SOD), glutathione (GSH), GSH peroxidase (GPx), GSH-S-transferase (GST)] except glutathione reductase (GR) were the highest in cytosol, but several fold lower in mitochondria and much lower in synaptosomes. However, FC synaptosomes from PD brains had significantly higher levels of GSH (p = 0.01) and related enzymes [GPx (p = 0.02), GR (p = 0.06), GST (p = 0.0001)] compared to controls. Conversely, mitochondria from the FC of PD cases displayed elevated SOD activity (p = 0.02) while the GSH and related enzymes were relatively unaltered. These changes in the neuropil fractions were associated with unchanged or lowered oxidative damage. Further, the mitochondrial content in the synaptosomes of both PD and control brains was ≥five-fold lower compared to the non-synaptic mitochondrial fraction. Altered distribution of oxidant/antioxidant markers in the neuropil fractions of the human brain during aging and PD has implications for (1) degenerative and protective mechanisms (2) distinct antioxidant mechanisms in synaptic terminals compared to other compartments.     

Protective Effects of Resveratrol on Hydrogen Peroxide Induced Toxicity in Primary Cortical Astrocyte Cultures

It is well established that the brain is particularly susceptible to oxidative damage due to its high consumption of oxygen and that astrocytes are involved in a variety of important activities for the nervous system, including a protective role against damage induced by reactive oxygen species (ROS). The use of antioxidant compounds, such as polyphenol resveratrol found in red wine, to improve endogenous antioxidant defenses has been proposed for neural protection. The aim of this study is to evaluate the putative protective effect of resveratrol against acute H₂O₂-induced oxidative stress in astrocyte cultures, evaluating ROS production, glutamate uptake activity, glutathione content and S100B secretion. Our results confirm the ability of resveratrol to counteract oxidative damage caused by H₂O₂, not only by its antioxidant properties, but also through the modulation of important glial functions, particularly improving glutamate uptake activity, increasing glutathione content and stimulating S100B secretion, which all contribute to the functional recovery after brain injury.     

Induction of theEscherichia coli UVM response by oxidative stress

UVM (ultravioletmodulation of mutagenesis) is a recently describedrecA-independent, inducible mutagenic phenomenon in which prior UV irradiation ofEscherichia coli cells strongly enhances mutation fixation at a site-specific 3-N⁴-ethenocytosine (C) lesion borne on a transfected single-stranded M13 DNA vector. Subsequent studies demonstrated that UVM is also induced by alkylating agents, and is distinct from both the SOS response and the adaptive response to alkylation damage. Because of the increasing significance being attributed to oxidative DNA damage, it is interesting to ask whether this class of DNA damage can also induce UVM. By transfecting M13 vector DNA bearing a site-specificC lesion into cells pretreated with inducing agents, we show here that the oxidative agent H₂O₂ is a potent inducer of UVM, and that the induction of UVM by H₂O₂ does not requireoxyR-regulated gene expression. UVM induction by H₂O₂ appears to be mediated by DNA damage, as indicated by the observation of a concomitant reduction in cellular toxicity and UVM response in OxyR^c cells. Available evidence suggests that UVM represents a generalized cellular response to a broad range of chemical and physical genotoxicants, and that DNA damage constitutes the most likely signal for its induction.