Oxidative events in neuronal and glial cell-enriched fractions of rat cerebral cortex

Zinc attenuates ecstasy-induced apoptosis through downregulation of caspase-3 in cultured TM3 cells: An experimental study

Background

3, 4-Methylenedioxymethamphetamine (MDMA) is commonly known as the most famous amphetamine derivative.

Objective

To evaluate the influence of zinc on MDMA-induced apoptosis and caspase- 3 gene expression in Leydig cell line (TM3).

Materials and Methods

Leydig cells were studied in differenet treatment groups regarding MDMA (0, 0.5, 1, 3, 5 mM) and zinc (0, 4, 8, 16, 32 μM). By the way, the effective concentration was determined to be 5 mM for MDMA and 8 μM for zinc. Then, TM3 cells were cultured in free medium as control (group I), medium containing MDMA (5 mM) (group II), zinc (8 µM) (group III), and zinc (8 µM) prior to MDMA (5 mM) (group IV) as well as in an untreated group (control). Cell viability was assessed at different times after cell culture by MTT assay. The mRNA expression level of caspase-3 was analyzed using real-time quantitative polymerase chain reaction.

Results

The cellular viability was significantly reduced in TM3 cells after 24 hr and 48 hr exposure time regarding different concentrations of MDMA as well as high concentration of zinc (16 and 32 μM). Cell viability was increased in the group that received zinc (8 µM) before addition of MDMA (5 mM) compared to the control and MDMA groups. The mean ± SE of fold was 22.40 ± 7.5, 0.06 ± 0.02, and 0.009 ± 0.003 in MDMA, zinc, and zinc + MDMA groups, respectively. The mean of caspase-3 mRNA level was significantly increased in the MDMA-treated group (5 mM), while the relative expression of caspase-3 gene was significantly decreased in the zinc (8 µM) + MDMA (5 mM) group compared with the MDMA (5 mM) group (p = 0.001).

Conclusion

Dietary intake of zinc has a protective effect against MDMA consumption in mouse.

Simvastatin protects ischemic spinal cord injury from cell death and cytotoxicity through decreasing oxidative stress: in vitro primary cultured rat spinal cord model under oxygen and glucose deprivation-reoxygenation conditions

Background

Ischemia and the following reperfusion damage are critical mechanisms of spinal cord injury. Statins have been reported to decrease ischemia–reperfusion injury in many organs including the spinal cord. Anti-oxidative effect is one of the main protective mechanisms of statin against neuronal death and cytotoxicity. We hypothesized that statins’ anti-oxidative property would yield neuroprotective effects on spinal cord ischemia–reperfusion injury

Methods

Primary cultured spinal cord motor neurons were isolated from Sprague–Dawley rat fetuses. Ischemia–reperfusion injury model was induced by 60 min of oxygen and glucose deprivation (OGD) and 24 h of reoxygenation. Healthy and OGD cells were treated with simvastatin at concentrations of 0.1, 1, and 10 μM for 24 h. Cell viability was assessed using water-soluble tetrazolium salt (WST)-8, cytotoxicity with LDH, and production of free radicals with DCFDA (2′,7′-dichlorofluorescein diacetate).

Results

OGD reduced neuronal viability compared to normoxic control by 35.3%; however, 0.1–10 μM of simvastatin treatment following OGD improved cell survival. OGD increased LDH release up to 214%; however, simvastatin treatment attenuated its cytotoxicity at concentrations of 0.1–10 μM (p < 0.001 and p = 0.001). Simvastatin also reduced deteriorated morphological changes of motor neurons following OGD. Oxidative stress was reduced by simvastatin (0.1–10 μM) compared to untreated cells exposed to OGD (p < 0.001).

Conclusions

Simvastatin effectively reduced spinal cord neuronal death and cytotoxicity against ischemia–reperfusion injury, probably via modification of oxidative stress.

STAMP2 increases oxidative stress and is critical for prostate cancer

The six transmembrane protein of prostate 2 (STAMP2) is an androgen-regulated gene whose mRNA expression is increased in prostate cancer (PCa). Here, we show that STAMP2 protein expression is increased in human PCa compared with benign prostate that is also correlated with tumor grade and treatment response. We also show that STAMP2 significantly increased reactive oxygen species (ROS) in PCa cells through its iron reductase activity which also depleted NADPH levels. Knockdown of STAMP2 expression in PCa cells inhibited proliferation, colony formation, and anchorage-independent growth, and significantly increased apoptosis. Furthermore, STAMP2 effects were, at least in part, mediated by activating transcription factor 4 (ATF4), whose expression is regulated by ROS. Consistent with in vitro findings, silencing STAMP2 significantly inhibited PCa xenograft growth in mice. Finally, therapeutic silencing of STAMP2 by systemically administered nanoliposomal siRNA profoundly inhibited tumor growth in two established preclinical PCa models in mice. These data suggest that STAMP2 is required for PCa progression and thus may serve as a novel therapeutic target.

Respiration and substrate transport rates as well as reactive oxygen species production distinguish mitochondria from brain and liver

BACKGROUND

Aberrant mitochondrial function, including excessive reactive oxygen species (ROS) production, has been implicated in the pathogenesis of human diseases. The use of mitochondrial inhibitors to ascertain the sites in the electron transport chain (ETC) resulting in altered ROS production can be an important tool. However, the response of mouse mitochondria to ETC inhibitors has not been thoroughly assessed. Here we set out to characterize the differences in phenotypic response to ETC inhibitors between the more energetically demanding brain mitochondria and less energetically demanding liver mitochondria in commonly utilized C57BL/6J mice.

RESULTS

We show that in contrast to brain mitochondria, inhibiting distally within complex I or within complex III does not increase liver mitochondrial ROS production supported by complex I substrates, and liver mitochondrial ROS production supported by complex II substrates occurred primarily independent of membrane potential. Complex I, II, and III enzymatic activities and membrane potential were equivalent between liver and brain and responded to ETC. inhibitors similarly. Brain mitochondria exhibited an approximately two-fold increase in complex I and II supported respiration compared with liver mitochondria while exhibiting similar responses to inhibitors. Elevated NADH transport and heightened complex II-III coupled activity accounted for increased complex I and II supported respiration, respectively in brain mitochondria.

CONCLUSIONS

We conclude that important mechanistic differences exist between mouse liver and brain mitochondria and that mouse mitochondria exhibit phenotypic differences compared with mitochondria from other species.

GM1 ganglioside activates ERK1/2 and Akt downstream of Trk tyrosine kinase and protects PC12 cells against hydrogen peroxide toxicity

Ganglioside GM1 at micro- and nanomolar concentrations was shown to increase the viability of pheochromocytoma PC12 cells exposed to hydrogen peroxide and diminish the accumulation of reactive oxygen species and oxidative inactivation of Na(+),K(+)-ATPase, the effects of micromolar GM1 being more pronounced than those of nanomolar GM1. These effects of GM1 were abolished by Trk receptor tyrosine kinase inhibitor and diminished by MEK1/2, phosphoinositide 3-kinase and protein kinase C inhibitors. Hydrogen peroxide activates Trk tyrosine kinase; Akt and ERK1/2 are activated downstream of this protein kinase. GM1 was found to activate Trk receptor tyrosine kinase in PC12 cells. GM1 (100 nM and 10 µM) increased the basal activity of Akt, but did not change Akt activity in cells exposed to hydrogen peroxide. Basal ERK1/2 activity in PC12 cells was increased by GM1 at a concentration of 10 µM, but not at nanomolar concentrations. Activation of ERK1/2 by hydrogen peroxide was enhanced by GM1 at a concentration of 10 µM and to a lesser extent at a concentration of 100 nM. Thus, the protective and metabolic effects of GM1 ganglioside on PC12 cells exposed to hydrogen peroxide appear to depend on the activation of Trk receptor tyrosine kinase and downstream activation of Akt and ERK1/2.

Mitochondrial electron transport chain in heavy metal-induced neurotoxicity: effects of cadmium, mercury, and copper

To clarify the role of mitochondrial electron transport chain (mtETC) in heavy-metal-induced neurotoxicity, we studied action of Cd²⁺, Hg²⁺, and Cu²⁺ on cell viability, intracellular reactive oxygen species formation, respiratory function, and mitochondrial membrane potential of rat cell line PC12. As found, the metals produced, although in a different way, dose- and time-dependent changes of all these parameters. Importantly, Cd²⁺ beginning from 10 [mu]M and already at short incubation time (3 h) significantly inhibited the FCCP-uncoupled cell respiration; besides, practically the complete inhibition of the respiration was reached after 3 h incubation with 50 [mu]M Hg²⁺ or 500 [mu]M Cd²⁺, whereas even after 48 h exposure with 500 [mu]M Cu²⁺, only a 50% inhibition of the respiration occurred. Against the Cd²⁺-induced cell injury, not only different antioxidants and mitochondrial permeability transition pore inhibitors were protective but also such mtETC effectors as FCCP and stigmatellin (complex III inhibitor). However, all mtETC effectors used did not protect against the Hg²⁺- or Cu²⁺-induced cell damage. Notably, stigmatellin was shown to be one of the strongest protectors against the Cd²⁺-induced cell damage, producing a 15–20% increase in the cell viability. The mechanisms of the mtETC involvement in the heavy-metal-induced mitochondrial membrane permeabilization and cell death are discussed.

The effect of pretreatment or combined treatment of quercetin on menadione toxicity in rat primary mixed glial cells in vitro

Neurons and glia are highly susceptible to reactive oxygen species that play a key role in various neurodegenerative diseases. Menadione, a synthetic derivative of vitamin K, induces reactive oxygen generation. Quercetin one of the most ubiquitous bioflavonoids in food of plant origin, has strong antioxidant activities on different cell types, however recent studies demonstrated that it has also prooxidant and cytotoxic potentials. We examined the action of pre- and co-treatment of quercetin on menadione induced glial toxicity. The primary mixed glial cells obtained from 1 to 3 day old rat brain were pretreated with 10, 25, 100 or 250 muM quercetin for 1 h, washed out and 10, 25, 50, 75 or 100 muM menadione was added for 6 h. The other group of cells was treated with respective doses of quercetin combined simultaneously with the same doses of menadione for 6 h. The cells were washed and incubated for additional 24 h for recovery period and the viability was measured by using MTT assay. Menadione was dose-dependently toxic to glia cells and pretreatment with respective quercetin doses for 1 h could not eliminate this toxicity. Although 10 and 25 muM quercetin combined with 10 and 25 muM menadione could not change, 100 and 250 muM quercetin together with 10 or 25 muM menadione for 6 h increased further the menadione induced toxicity. We conclude that when combined with menadione, quercetin at high doses could be toxic to primary rat glia cells in culture.

Protective and antioxidative effects of GM1 ganglioside in PC12 cells exposed to hydrogen peroxide are mediated by Trk tyrosine kinase

GM1 ganglioside was found to increase the survival of PC12 cells exposed to H(2)O(2), its action was blocked by Trk tyrosine kinase inhibitor K-252a. Thus, the inhibition of H(2)O(2) cytotoxic action by GM1 constituted 52.8 +/- 4.3%, but in the presence of 1.0 microM K-252a it was only 11.7 +/- 10.8%, i.e. the effect of GM1 became insignificant. Exposure to GM1 markedly reduced the increased accumulation of reactive oxygen species (ROS) and diminished the inactivation of Na(+),K(+)-ATPase induced in PC12 cells by H(2)O(2), but in the presence of K-252a GM1 did not change these metabolic parameters. The inhibitors of extracellular signal-regulated protein kinase, phosphatidyl inositol 3-kinase and protein kinase C decreased the effects of GM1. A combination of these protein kinase inhibitors reduced inhibition of H(2)O(2) cytotoxic action by GM1 to the larger extent than each of the inhibitors and practically abolished the ability of GM1 to decrease H(2)O(2)-induced ROS accumulation. The protective and antioxidative effects of GM1 in PC12 cells exposed to H(2)O(2) appear to be mediated by activation of Trk receptor tyrosine kinase and the protein kinases downstream from this enzyme.

Epigallocatechin-3-gallate induced primary cultures of rat hippocampal neurons death linked to calcium overload and oxidative stress

Epigallocatechin-3-gallate (EGCG), a catechin polyphenols component, is the main ingredient of green tea extract. It has been reported that EGCG is a potent antioxidant and beneficial in oxidative stress-related diseases, but others and our previous study showed that EGCG has pro-oxidant effects at high concentration. Thus, in this study, we tried to examine the possible pathway of EGCG-induced cell death in cultures of rat hippocampal neurons. Our results showed that EGCG caused a rapid elevation of intracellular free calcium levels ([Ca(2+)](i)) in a dose-dependent way. Exposure to EGCG dose- and time-dependently increased the production of reactive oxygen species (ROS) and reduced mitochondrial membrane potential (Deltapsi(m)) as well as the Bcl-2/Bax expression ratio. Importantly, acetoxymethyl ester of 5,5'-dimethyl-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, ethylene glycol-bis-(2-aminoethyl)-N,N,N',N'-tetraacetic acid, and vitamin E could attenuate EGCG-induced apoptotic responses, including ROS generation, mitochondrial dysfunction, and finally partially prevented EGCG-induced cell death. Furthermore, treatment of hippocampal neurons with EGCG resulted in an elevation of caspase-3 and caspase-9 activities with no significant accompaniment of lactate dehydrogenase release, which provided further evidence that apoptosis was the dominant mode of EGCG-induced cell death in cultures of hippocampal neurons. Taken together, these findings indicated that EGCG induced hippocampal neuron death through the mitochondrion-dependent pathway.

Effects of different concentrations of oxygen-ozone on rats' astrocytes in vitro

Although the widespread use of the oxygen-ozone in pain management, there is currently no consensus on its mechanisms of action and nearly no report for its action on nervous cells. Accordingly, the present study was designed to assess the effects of oxygen-ozone on astrocytes. Astrocytes were cultured in vitro through methods of trypsinization, different-speed cultivation and passaging to purify, then seeded into 24 well plates and divided to one of four groups (n=7) to receive the following treatments: respectively added 400 microl complete medium (CM) after effects of 20 microg/ml oxygen-ozone (Group O-20), 40 microg/ml oxygen-ozone (Group O-40), 60 microg/ml oxygen-ozone (Group O-60); without intervention (Group C). After incubation of 2 h or 4 h, cell morphology was observed and endocellular superoxide dismutase (SOD), endocellular malondialdehyde (MDA), lactate dehydrogenase (LDH) leaking ratio, and dead cells' percentage were detected. The results showed cell damage in Group O-60. As compared with Group C, endocellular SOD increased in all groups, MDA at 2 h increased in Groups O-40 and O-60 and MDA at 4 h decreased in Groups O-20 and O-40; LDH leaking ratio at 2 h in Group O-20 and those at 2 and 4 h in Group O-40 decreased, while LDH leaking ratio at 4 h increased and dead cells' percentage in Group O-60 increased. We conclude that in short time (2 and 4 h), oxygen-ozone of 60 microg/ml showed a damaging role on astrocytes in vitro, while oxygen-ozone of 20 and 40 microg/ml did not show damaging role obviously.

Exercise intensity influences cell injury in rat hippocampal slices exposed to oxygen and glucose deprivation

We evaluated the effects of two levels of daily forced exercise intensity (moderate and high) in the treadmill over cell susceptibility to oxygen and glucose deprivation (OGD) in hippocampal slices from Wistar rats. Moderate exercise decreased lactate dehydrogenase (LDH) release after OGD, while a significant increase in LDH release was observed in the high intensity group submitted to OGD. Our data corroborate the hypothesis that higher training intensity exacerbates brain damage, while a moderate intensity reduces the injury caused by in vitro ischemia.

Neuroprotective effect of N-acetyl cysteine on hypoxia-induced oxidative stress in primary hippocampal culture

Hippocampus has received a considerable attention in the recent past due to its role in a number of important functions such as learning and memory. The effect of hypoxia on neuronal cell injury especially on hippocampal cells is not well known. The aim of the present study was to characterize the biochemical changes in primary cultured hippocampal neurons during hypoxic exposure and the protective effect of N-acetyl cysteine on hypoxia-induced cytotoxicity. The hippocampal culture grown in 24-well plates was exposed to hypoxia for 3 h in a dessicator in 95% N(2), 5% CO(2) atmosphere at 37 degrees C. Later, the cells were allowed to recover for 1 h under normoxia. It was observed that there is an appreciable increase in cytotoxicity in cells exposed to hypoxia. Further, there was a significant decrease in mitochondrial membrane potential and appreciable increase in reactive oxygen species and single-strand DNA breaks in cells exposed to hypoxia compared to control. There is a significant fall in glutathione peroxidase, glutathione reductase, reduced glutathione levels, and nitric oxide in the cells exposed to hypoxia. Significant elevation in the intracellular calcium level in the cells on exposure to hypoxia was observed. Supplementation with NAC (50 microM) resulted in a significant cytoprotection, fall in ROS generation, and higher antioxidant levels similar to that of control cells. NAC also inhibited DNA strand breaks induced by hypoxia. The study indicates that NAC has significant neuroprotective activity during hypoxia in primary hippocampal culture.

Newborn neurons acquire high levels of reactive oxygen species and increased mitochondrial proteins upon differentiation from progenitors

A population of embryonic rat cortical cells cultured in the presence of FGF2 and having neuronal morphology expressed higher levels of reactive oxygen species (ROS) than did progenitor cells, astrocytes, and several cell lines of neuronal and non-neuronal origin. ROS were assessed using 5-(and-6)-chlormethyl-2',7'-dichlorodihydrofluorescein diacetate, acetyl ester (CM-H2DCF-DA), and high levels persisted in the presence of antioxidants or lowered levels of ambient oxygen. Greater than 95% of high ROS-producing cells, isolated by fluorescence-activated cell sorting, expressed the neuronal marker beta III tubulin. These cells did not incorporate BrdU or express nestin, unlike low ROS-producing cells, 99% of which exhibited both of these characteristics. Upon growth factor removal, low ROS-expressing cells differentiated into neurons and astrocytes and these neurons expressed high levels of ROS, indicating that ROS accumulation accompanies the differentiation of progenitors into neurons. ROS levels were decreased by added superoxide dismutase and catalase, suggesting that both superoxide and hydrogen peroxide contribute to the ROS signal. High ROS-expressing cells also contained higher levels of several mitochondrial respiratory chain components. Although ROS have been associated with conditions that lead to cell death, our results and recent studies on the role of ROS as regulators of signal pathways are consistent with the possibility that ROS play a role in the development of the neuronal phenotype. Moreover, the differential production of ROS provides a useful method to isolate from mixed populations cells that are highly enriched for either progenitor cells or neurons.

Friedreich ataxia: the oxidative stress paradox

Friedreich ataxia (FRDA) results from a generalized deficiency of mitochondrial and cytosolic iron-sulfur protein activity initially ascribed to mitochondrial iron overload. Recent in vitro data suggest that frataxin is necessary for iron incorporation in Fe-S cluster (ISC) and heme biosynthesis. In addition, several reports suggest that continuous oxidative damage resulting from hampered superoxide dismutases (SODs) signaling participates in the mitochondrial deficiency and ultimately the neuronal and cardiac cell death. This has led to the use of antioxidants such as idebenone for FRDA therapy. To further discern the role of oxidative stress in FRDA pathophysiology, we have tested the potential effect of increased antioxidant defense using an MnSOD mimetic (MnTBAP) and Cu,ZnSOD overexpression on the murine FRDA cardiomyopathy. Surprisingly, no positive effect was observed, suggesting that increased superoxide production could not explain by itself the FRDA cardiac pathophysiology. Moreover, we demonstrate that complete frataxin-deficiency neither induces oxidative stress in neuronal tissues nor alters the MnSOD expression and induction in the early step of the pathology (neuronal and cardiac) as previously suggested. We show that cytosolic ISC aconitase activity of iron regulatory protein-1 progressively decreases, whereas its apo-RNA binding form increases despite the absence of oxidative stress, suggesting that in a mammalian system the mitochondrial ISC assembly machinery is essential for cytosolic ISC biogenesis. In conclusion, our data demonstrate that in FRDA, mitochondrial iron accumulation does not induce oxidative stress and we propose that, contrary to the general assumption, FRDA is a neurodegenerative disease not associated with oxidative damage.

Oxidative stress-induced death in the nervous system: cell cycle dependent or independent?

Neuronal death, attributable to perturbed redox homeostasis, is the underlying factor in many acute and chronic neurological disorders. The mechanisms employed by oxidatively stressed neurons to commit to cell death pathways are beginning to be characterized, but this is hampered by a lack of good models that extrapolate readily to redox-dependent neuronal death paradigms. In this Mini-Review, we discuss mechanisms by which oxidative stress can result in neurodegeneration. We examine evidence on which terminally differentiated neurons might commit to death under conditions of oxidative stress. In some cases, death may be linked to an aberrant and uncoordinated reentry into the cell cycle and mitotic catastrophe. Other evidence suggests that cell cycle reentry is not mandatory for death execution. Rather, the reexpression of cell cycle proteins may induce apoptotic pathways in a cell cycle-independent manner. In contrast to these models, there is also evidence that oxidative neuronal death is independent of cell cycle proteins. We conclude that oxidative stress-induced neuronal death may be promoted via several pathways, which may be cycle protein dependent or independent. The determining factor for which or how many pathways are induced appears to be context dependent and determined by the level and duration of oxidative stress.

Age-related susceptibility to oxygen and glucose deprivation damage in rat hippocampal slices

Aging is an important risk factor for stroke. We evaluated the effects of aging on cell susceptibility to oxygen and glucose deprivation (OGD) in slices of the hippocampus from Wistar rats aged 2, 11 and 24 months. Lactate dehydrogenase (LDH) released to the incubation media and free radical content were markedly increased in the 24-month group submitted to OGD. These results confirm that hippocampal tissue from old animals is more susceptible to ischemia-reoxygenation injury.

Activation of cytosolic phospholipase A2 in Her14 fibroblasts by hydrogen peroxide: a p42/44MAPK-dependent and phosphorylation-independent mechanism

Reactive oxygen species (ROS) have been implicated in the pathogenesis of diseases as well as various normal cellular processes. It has been suggested that ROS function as mediators of signal transduction, given that they can mimic growth factor-induced signaling. The ROS H2O2 has been reported to activate phospholipase A2 (PLA2) and, therefore, we investigated if and through which pathway ROS activate cytosolic PLA2 (cPLA2) in Her14 fibroblasts. cPLA2 was activated concentration-dependently by H2O2 in a transient manner. In addition, the lipophilic cumene hydroperoxide was shown to induce cPLA2 activity in the same manner. H2O2-induced cPLA2 activity in Her14 cells was partially phosphorylation-dependent, which was mediated through the Raf-MEK-p42/44(MAPK) pathway and occurred partially through a phosphorylation-independent mechanism. ROS can lead to changes in the (micro) viscosity of membranes due to the presence oxidized lipids, thereby increasing the substrate availability for cPLA2. In support of this, treatment of Her14 cells with H2O2 induced lipid peroxidation time-dependently as determined from degradation of lipid arachidonate and linoleate and the formation of aldehydic degradation products. Furthermore, H2O2 induced translocation of cPLA2 to the membrane fraction in a calcium-independent fashion, with a concomitant increase in cPLA2 activity. Collectively, the results suggest that oxidative stress-induced cPLA2 activity is partially phosphorylation-dependent and is further increased due to increased substrate availability by the action of ROS on membranes.

Oxidative stress in rat cortical neurons and astrocytes induced by paraquat in vitro

Oxidative stress has been discussed as crucial mechanism of neuronal cell death in the adult brain. However, it was not clear until now whether neurons are more sensitive to oxidative stress than the other cells in the brain, e.g. astrocytes. Therefore both cell types were exposed to oxidative stress provoked by the redox-cycling compound paraquat. Cortical neurons were found to be more sensitive towards paraquat toxicity than astrocytes as shown by MTT and Neutral Red assay, two different cytotoxicity assays. Mitochondrial functions were determined by the mitochondrial membrane potential and intracellular ATP concentrations. Again cortical neurons were more severely impaired (by paraquat than astrocytes). The production of reactive oxygen species after paraquat exposure was much higher in cortical neurons than in astrocytes and correlated with a higher depletion of GSH (intracellular glutathion). Lipid peroxidation could be shown in astrocytes via the breakdown product malondialdehyde (MDA) whereas in cortical neurons 4-hydroxynonenal (4-HNE) was detected as this endpoint. If and how oxidative stress influences the antioxidant defense was determined via changes in the expression of antioxidant enzymes. Paraquat exposure lead to a 2-3 fold increase of catalase, MnSOD and CuZnSOD mRNA expression in astrocytes. In contrast to astrocytes, in cortical neurons catalase and MnSOD mRNA levels were only marginally elevated above 1.5-fold by treatment with paraquat. Expression levels of glutathione peroxidase (GPx) mRNA were the only one that were not changed in both cell types after paraquat exposure. It is concluded that the more marked increase in expression levels of antioxidant enzymes may render astrocytes more resistant to oxidative stress than neuronal cells.

Intracellular generation of free radicals and modifications of detoxifying enzymes in cultured neurons from the developing rat forebrain in response to transient hypoxia

To address the influence of oxidative stress and defense capacities in the effects of transient hypoxia in the immature brain, the time course of reactive oxygen species generation was monitored by flow cytometry using dihydrorhodamine 123 and 2',7'-dichlorofluorescein-diacetate in cultured neurons issued from the fetal rat forebrain and subjected to hypoxia/reoxygenation (6 h/96 h). Parallel transcriptional and activity changes of superoxide dismutases, glutathione peroxidase and catalase were analyzed, in line with cell outcome. The study confirmed hypoxia-induced delayed apoptotic death, and depicted increased mitochondrial and cytosolic productions of free radicals (+30%) occurring over the 48-h period after the restoration of oxygen supply, with sequential stimulations of superoxide dismutases. Whereas catalase mRNA levels and activity were augmented by cell reoxygenation, glutathione peroxidase activity was transiently repressed (-24%), along with reduced glutathione reductase activity (-27%) and intracellular glutathione depletion (-19%). Coupled with the neuroprotective effects of the glutathione precursor N-acetyl-cysteine (50 microM), these data suggest that hypoxia/reoxygenation-induced production of reactive oxygen species can overwhelm glutathione-dependent antioxidant capacity, and thus may contribute to the resulting neuronal apoptosis.

Glucose-6-phosphate dehydrogenase supports the functioning of the synapses in rat cerebellar cortex

This study investigates heterogeneous glucose-6-phosphate dehydrogenase (G6PD) expression in the rat cerebellar cortex. G6PD activity and its electrophoretic pattern, evaluated on the cerebellar homogenate, were found to be similar to those of other brain areas. However, histochemical and immunohistochemical analyses revealed that the highest expression of G6PD activity and protein was in Purkinje's cells, followed by the molecular and granular layers. Electron microscopy analysis showed that, in Purkinje's cells, the G6PD reaction products were concentrated in the neurites while in the basket cells in the cell body. The granules showed a weaker activity everywhere. The quantitative distribution of G6PD is discussed in the light of the neurochemical function of these cells.

Free radical production and changes in superoxide dismutases associated with hypoxia/reoxygenation-induced apoptosis of embryonic rat forebrain neurons in culture

Following hypoxia/reoxygenation (6h/96h), cultured neurons from the embryonic rat forebrain undergo delayed apoptosis. To evaluate the participation of oxidative stress and defense mechanisms, temporal evolution of intraneuronal free radical generation was monitored by flow cytometry using dihydrorhodamine 123, in parallel with the study of transcriptional, translational, and activity changes of the detoxifying enzymes Cu/Zn-SOD and Mn-SOD. Two distinct peaks of radical generation were depicted, at the time of reoxygenation (+ 27%) and 48 h later (+ 25%), respectively. Radical production was unaffected by caspase inhibitors YVAD-CHO or DEVD-CHO, which prevented neuronal damage, suggesting that caspase activation is not an upstream initiator of radicals in this model. Cell treatment by vitamin E (100 microM) displayed significant neuroprotection, whereas the superoxide generating system xanthine/xanthine oxidase induced apoptosis. Transcript and protein levels of both SODs were reduced 1 h after the onset of hypoxia, but activities were transiently stimulated. Reoxygenation was associated with an increased expression (139%), but a decreased activity (21%) of the inducible Mn-SOD, whereas Cu/Zn-SOD protein and activity were low and progressively increased until 48 h post-hypoxia, when the second rise in radicals occurred. In spite of a temporal regulation of SODs, which parallels radical formation, oxidative stress might account for neurotoxicity induced by hypoxia.

Adeno-associated virus mediated gene transfer into primary rat brain neuronal and glial cultures: enhancement with the pH-sensitive surfactant dodecyl 2-(1'-imidazolyl) propionate

This study evaluated the effects of a novel, pH-sensitive surfactant, dodecyl 2-(1'-imidazolyl) propionate (DIP), on cationic lipid mediated transfection in primary rat brain neuronal and glial cultures. The cationic lipid complex DOTAP/DOPE (1, 2-dioleoyl-3-trimethylammonium propionate and dioleoyl phosphatidylethanolamine, respectively) was added over a range of concentrations (0-120 microg/ml) with DNA concentration kept constant (1.6 microg/ml). The neuron-specific enolase (NSE) and cytomegalovirus (CMV) promoters were found to drive green fluorescent protein (GFP) expression in neuron-enriched and glial cultures, respectively, using adeno-associated virus (AAV) derived constructs. NSE-driven GFP expression was not observed in glial cultures. Addition of DOTAP/DOPE increased transfection efficiency over a wide range of lipid concentrations (5-50 microg/ml) keeping DNA concentration constant (1.6 microg/ml). Addition of DIP to the lipid/DNA complex increased maximum transfection efficiencies in glial and neuronal cultures 2-3-fold. Transfection efficiencies were at their maximum with a similar total lipid concentration (50 microg/ml) in both cell-types in the presence of DIP. Neuronal cultures were more sensitive than glia to the toxic actions of DOTAP/DOPE, with or without DIP. These results indicate that AAV-mediated gene-transfer to neurons and glia can be facilitated by addition of a pH-sensitive surfactant to cationic liposome/DNA complexes and that endosomal escape could be a limiting factor in transgene expression.

Astrocytes prevent neuronal death induced by reactive oxygen and nitrogen species

Reactive oxygen and nitrogen species (RO/NS) such as nitric oxide (NO), hydroxyl radical (OH.), and superoxide anion (O(2)(-)) are generated in a variety of neuropathological processes and damage neurons. In the present study, we investigated the neuroprotective effects of rat astrocytes against RO/NS-induced damage using neuron-glia cocultures, and the effects were compared to those of microglial cells. Sodium nitroprusside (SNP), 3-morpholinosydnonimine (SIN-1), and FeSO(4) were used to generate NO, O(2)(-) and NO, and OH., respectively. Solely cultured neurons, which were transiently exposed to these agents, degenerated, possibly through apoptotic mechanisms as revealed by in situ detection of DNA fragmentation, whereas neurons cocultured with either astrocytes or microglial cells were viable even after exposure to RO/NS. In contrast, most neurons cocultured with meningeal fibroblasts degenerated. Astrocyte-conditioned medium partially attenuated RO/NS-induced neuronal damage. When neurons were cultured on astrocyte-derived extracellular matrix (AsECM), neuronal death induced by SNP and FeSO(4) was almost completely inhibited. AsECM contained significant amounts of laminin and fibronectin, and pure fibronectin and laminin also protected neurons against RO/NS-induced damage in the same manner as AsECM. These results suggest that astrocytes can protect neurons against RO/NS-induced damage by secreting soluble and insoluble factors.

Superoxide production by primary rat cerebral endothelial cells in response to pneumococci

Animal studies of experimental bacterial meningitis have provided evidence for an involvement of reactive oxygen species (ROS) in the pathophysiology of this disease. Using a lucigenin-enhanced chemiluminescence (CL) method, we tested whether primary rat cerebral endothelial cells can be induced to release ROS upon stimulation with pneumococci. In addition, we determined CSF levels of two markers of lipid peroxidation in patients with bacterial meningitis, compared to patients with viral meningitis and noninflammatory neurological disorders. Malondialdehyde/4-hydroxynonenal concentrations were significantly elevated in CSF samples obtained from patients with bacterial meningitis (23.12+/-5.47 microM), as compared to both control groups (5.43+/-0.18 microM and 7.80+/-0.33 microM, respectively). Cerebromicrovascular endothelial cells, granulocytes, and the macrophage cell line RAW 264.7 (but not astrocytes and neuron-like cells) produced an increase in CL intensity after stimulation with pneumococci. The peak value produced by endothelial cells (500+/-83 cpm) was significantly lower than the maximum CL response in macrophages (1386+/-142 cpm; p<0.05). After addition of superoxide dismutase (SOD), the CL signal returned to baseline values. Equal to the CL technique, nitroblue tetrazolium (NBT) staining of RAW 264.7 showed SOD-inhibitable formazan precipitation when stimulated with pneumococci. In conclusion, this study suggests an important role of endothelial cells in the pathophysiology of bacterial meningitis-namely as a source for ROS production.

The effects of oxidative stress in in vitro cultured astroglial cells

It has been suggested that glial cells in the central nervous system might function as a buffer and protect neurons and synapses. Associated with such a function, glial cells might be affected in degenerative diseases, for example, Alzheimer's disease and Parkinson's disease, due to generation of free-radicals. Free-radicals might be generated during the metabolic transformation of xenobiotics. The purpose of the present study was to determine whether a xenobiotic (in this case, paraquat), is metabolised in glial cells during the generation of free-radicals. Furthermore, this study determined whether free-radicals can induce DNA fragmentation and whether this fragmentation can be repaired. The data produced indicated that astroglial cells contain P450-reductase which transforms paraquat into a pyridium free-radical. In turn, this causes a dose-dependent DNA fragmentation, as determined by using single-cell gel electrophoresis. The dose-dependent effect was valid up to 80μM paraquat. The oxidative stress induced in the astroglial cells was also associated with a maximum 15% increase in the anti-oxidative enzyme, glutathione peroxidase. After exposure to 40μM paraquat, followed by growth of the cells in a paraquat-free medium, DNA repair was shown to be rather slow, and was only obvious two hours after exposure to paraquat. This might be related the shuttle in which paraquat/P450-reductase is implicated, which causes a protracted generation of free-radicals. The data are discussed in relation to the available literature.

Abnormalities of retinal metabolism in diabetes or experimental galactosemia. VI. Comparison of retinal and cerebral cortex metabolism, and effects of antioxidant therapy

Metabolic abnormalities observed in retina and in cerebral cortex were compared in diabetic rats and experimentally galactosemic rats. Diabetes or experimental galactosemia of 2 months duration significantly increased oxidative stress in retina, as shown by elevation of retinal thiobarbituric acid reactive substances (TBARS) and subnormal activities of antioxidant defense enzymes, but had no such effect in the cerebral cortex. Activities of sodium potassium adenosine triphosphatase [(Na,K)-ATPase] and calcium ATPase became subnormal in retina as well as in cerebral cortex. In contrast, protein kinase C (PKC) activity was elevated in retina but not in cerebral cortex in the same hyperglycemic rats. Dietary supplementation with an antioxidant mixture (containing ascorbic acid, Trolox, alpha-tocopherol acetate, N-acetyl cysteine, beta-carotene, and selenium) prevented the diabetes-induced and galactosemia-induced elevation of retinal oxidative stress, the elevation of retinal PKC activity and the decrease of retinal ATPases. In cerebral cortex, administration of the antioxidant diet also prevented the diabetes-induced decreases in (Na,K)-ATPase and calcium ATPases, but had no effect on TBARS and activities of PKC and antioxidant-defense enzymes. The results indicate that retina and cerebral cortex differ distinctly in their response to elevation of tissue hexose, and that cerebral cortex is more resistant than retina to diabetes-induced oxidative stress. The greater resistance to oxidative stress in cerebral cortex, as compared to retina, is consistent with the resistance of cerebral cortex to microvascular disease in diabetes, and with a hypothesis that oxidative stress contributes to microvascular disease in diabetes. Dietary supplementation with these antioxidants offers a means to inhibit multiple hyperglycemia-induced retinal metabolic abnormalities.

Antioxidant status and alpha1-antiproteinase activity in subarachnoid hemorrhage patients

The antiproteasic activity of alpha1-antitrypsin (alpha1-AT) is reduced in cases of subarachnoid hemorrhage from ruptured intracranial aneurysm and particularly in patients currently smoking; alpha1-AT is very sensitive to oxidant agents. About 50% of physiological anti-oxidant systemic capacity is represented by Vitamin A, E and C. Plasmatic amounts of alpha1-AT, alpha1-AT Collagenase Inhibitory Capacity (CIC) and levels of vitamin A, vitamin E and vitamin C were analyzed in 39 patients, 26 women and 13 men, operated for intracranial aneurysm; 11 patients with unruptured intracranial aneurysm were considered as controls while 28 patients were included within 12 hours from subarachnoid hemorrhage (SAH). Plasmatic levels of vitamin A and vitamin E were significantly lower (p=0.038 and p=0.0158) in patients suffering SAH than in controls, while no statistically significant differences were found in mean plasmatic vitamin C levels. Level of alpha1-AT was not statistically different in controls and in patients with SAH; however, the activity of alpha1-AT, evaluated as CIC, is significantly reduced in patients with SAH (p=0.019). We have observed that systemic plasmatic levels of vitamins did not significantly differ in relation to smoking habit. Vitamin A and E represent an important defensive system against free radicals reactions. Particularly, vitamin E acts as an antioxidant by scavenging free-radicals. A reduced anti-oxidant status might be related to the higher sensibility of alpha1-AT to oxidative reactions and the activity of alpha1-AT is dependent on the antioxidant capacity of liposoluble vitamins. We can speculate that an acute systemic oxidative stress condition might influence the rupture of intracranial aneurysms.

Autoxidation of rat brain homogenate: evidence for spontaneous lipid peroxidation. Comparison with the characteristics of Fe2+- and ascorbic acid-stimulated lipid peroxidation

Aerobically-incubated brain homogenates are known to undergo autoxidation characterized by spontaneous TBARS production, presumably as a result of lipid peroxidation. However, TBARS measurement alone, because of its lack of specificity, is not sufficient to demonstrate the occurrence of lipid peroxidation in complex biological systems. This study, undertaken to determine whether or not spontaneous oxidation of rat brain homogenate is due to lipid peroxidation, measured different specific markers of this process (fatty acids, lipid aldehydes and the formation of fluorescence products) and studied changes in alpha-tocopherol. Incubation of rat brain homogenates at 37 degrees C under air led to spontaneous TBARS formation, which was accompanied by lipid aldehydes and lipid fluorescence products as well as polyunsaturated fatty acid (PUFA) degradation. Alpha-tocopherol was also consumed. On the whole, these results demonstrate that autoxidation of brain homogenate is a spontaneous lipid peroxidation process. When homogenates were exposed to Fe2+ and ascorbic acid-induced oxidative stress, lipid peroxidation was enhanced. However, spontaneous and stimulated peroxidation showed similar patterns not characteristic of classical lipid peroxidation, i.e. without the lag and accelerating phases typical of a propagating chain reaction. PUFA degradation was limited despite stimulation of peroxidation.

Mediation by arachidonic acid metabolites of the H2O2-induced stimulation of mitogen-activated protein kinases (extracellular-signal-regulated kinase and c-Jun NH2-terminal kinase)

Reactive oxygen species modulate major cellular functions by mechanisms which are still poorly understood. Recently, H2O2 has been reported to stimulate the activity of the mitogen-activated protein kinases (MAPKs) ERK and JNK, and the expression of the proto-oncogenes c-fos and c-jun. As their expression is enhanced by H2O2 in astrocytes, we studied whether these MAPKs were stimulated by H2O2 in primary cultured astrocytes. The result was positive, a maximum of stimulation being reached with 200 microM H2O2 (0.3 pmol H2O2/cell) for both ERK and JNK. ERK was previously reported to stimulate cytosolic phospholipase A2 phosphorylation and activity. H2O2 stimulated the release of arachidonic acid in astrocytes, as already reported in other cell types. We found also that cPLA2 phosphorylation was increased by H2O2. Moreover, the stimulation by H2O2 of ERK and JNK was decreased by phospholipase A2 activity inhibitors. When astrocytes were incubated first with eicosatetraynoic acid, a structural analogue competing in arachidonic acid metabolism, the stimulation of JNK by H2O was also inhibited, suggesting the involvement of arachidonic acid metabolites. Cyclooxygenase or cytochrome P450 monooxygenase inhibitors failed in decreasing the MAPK stimulation by H2O2, whereas lipoxygenase inhibitors completely abolished that of JNK. Mitogenicity has been reported to be stimulated by H2O2 in other cell types. Although ERK was strongly and durably stimulated by 200 microM H2O2 in astrocytes, at the same extent as by mitogenic growth factors, basal thymidine incorporation rate was decreased by more than 80% after 12-15 h. Moreover, the stimulation of thymidine incorporation induced by basic fibroblast growth factor was transiently abolished by H2O2. Furthermore, H2O2 likely induced the expression of CL100/PAC1/MKP-1, a dual specificity phosphatase which has been implicated in ERK and JNK inactivation in the nucleus. Finally, the prior treatment of astrocytes with MK886, a 5-lipoxygenase-activating protein inhibitor, prevented JNK from stimulation, but did not prevent thymidine incorporation from inhibition, both induced by H2O2. These results strongly suggest an involvement of arachidonic acid and/or its metabolites in the stimulation of both ERK and JNK following the oxidative stress evoked by H2O2, which induced a cell cycle arrest probably independent of the stimulation of JNK.

Glucose-6-phosphate dehydrogenase activity is higher in the olfactory bulb than in other brain areas

The activity of antioxidant enzymes was measured in the olfactory bulb (OB) of rat and compared with cortex, hippocampus, striatum and septum. Glutathione reductase, glutathione peroxidase, catalase and superoxide dismutase were not significantly different in the five brain areas, while glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase activities were four times higher in the OB than in the other areas. This picture prompted us to explore the reasons of the marked increase of G6PD, since it is the enzyme that regulates the operation of the hexose monophosphate shunt. A first approach was to analyze the G6PD electrophoretic pattern. The analysis revealed that the high G6PD activity of the bulb was neither due to new isoenzymes nor to a modification of the equilibrium between the G6PD dimers. We secondly hypothesized an induction of G6PD activity in the OB by oxidant stress. The assay of markers of the oxidant stress, such as thiobarbituric acid reactive substances, oxidized and reduced glutathione, did not confirm this hypothesis. A third approach was the cytochemical analysis of cryostat sections of OB. By this method we identified a particular cell type which was very rich in G6PD and located at the border of the glomerular layer. Thus, we attributed the high G6PD activity of the OB to the consistent presence of periglomerular cells, that probably need a high G6PD activity for their regulatory function in the neurochemical transmission.