The protective effect of vitamin E, idebenone and reduced glutathione on free radical mediated injury in rat brain synaptosomes

Insights into early pathogenesis of sporadic Alzheimer's disease: role of oxidative stress and loss of synaptic proteins

Oxidative stress, induced by impaired insulin signaling in the brain contributes to cognitive loss in sporadic Alzheimer's disease (sAD). This study evaluated early hippocampal oxidative stress, pre- and post-synaptic proteins in intraperitoneal (IP) and intracerebroventricular (ICV) streptozotocin (STZ) models of impaired insulin signaling. Adult male Wistar rats were injected with STZ, IP, or ICV, and sacrificed 1-, 3-, or 6-weeks post injection. Rat's cognitive behavior was assessed using Morris water maze (MWM) tests at weeks 3 and 6. Hippocampal synaptosomal fractions were examined for oxidative stress markers and presynaptic [synapsin I, synaptophysin, growth-associated protein-43 (GAP-43), synaptosomal-associated protein-25 (SNAP-25)] and postsynaptic [drebrin, synapse-associated protein-97 (SAP-97), postsynaptic density protein-95 (PSD-95)] proteins. IP-STZ and ICV-STZ treatment impaired rat's cognition, decreased the levels of reduced glutathione (GSH) and increased the levels of thiobarbituric acid reactive species (TBARS) in a time dependent manner. In addition, it reduced the expression of pre- and post-synaptic proteins in the hippocampus. The decline in cognition is significantly correlated with the reduction in synaptic proteins in the hippocampus. In conclusion, impaired insulin signaling in the brain is deleterious in causing early synaptosomal oxidative damage and synaptic loss that exacerbates with time and correlates with cognitive impairments. Our data implicates oxidative stress and synaptic protein loss as an early feature of sAD and provides insights into early biochemical and behavioral changes during disease progression.

Attenuative Role of Idebenone on Deltamethrin Mediated Peroxidative Toxicity of Ram Semen Stored at 4°C

The current study was conducted to evaluate the different concentrations of deltamethrin (DEL; Exp. 1) and the protective role of idebenone (IDB) supplemented with toxic dose of deltamethrin (Exp. 2) during chilled storage of ram semen. Collected samples were pooled and diluted at 500×106 spermatozoa per mL. In Exp. 1, effect of DEL at 1, 2.5, 5, 10, 20, 40, 80 μM levels was evaluated on different variables of spermatozoa motion characteristics. In Exp. 2, different amounts of IDB (2, 4, and 8 μM) concurrent with constant doses of DEL (10 μM) were examined on semen quality upon chilled preservation up to 72 h. Indices of spermatozoa kinematics, functionality of plasma membrane and viability were recorded. Biochemical metabolites were measured in spermatozoa and its medium (extender) at different time points. In Exp. 1, different parameters of spermatozoa kinematics were affected by exposure to DEL in a dose dependent manner. In Exp. 2, combination of IDB with DEL resulted in a significant (P<0.05) increase in total motility, forward progressive motility and curvilinear path velocity compared to DEL group at 24, 48 and 72 h. Simultaneous administration of IDB with DEL increased the percentage of spermatozoa with functional membrane and viability compared to DEL group at 72 h (P<0.05). The amounts of lipid peroxidation index were lower in medium of combination groups compared to DEL group at 48 h and 72 h (P<0.05). Antioxidant capacity was higher in spermatozoa and medium of IDB treated groups compared to DEL group at 72 h (P<0.05). Amounts of total nitrate-nitrite and superoxide dismutase activity of spermatozoa and medium were not affected by treatment (P>0.05). In conclusion, IDB could ameliorate oxidative and peroxidative damages induced by DEL mild toxicity upon cold preservation of ram semen.

Improving Sperm Oxidative Stress and Embryo Quality in Advanced Paternal Age Using Idebenone In Vitro-A Proof-of-Concept Study

Advanced paternal age is associated with increased sperm reactive oxygen species (ROS) and decreased fertilization and pregnancy rates. Sperm washing during infertility treatment provides an opportunity to reduce high sperm ROS concentrations associated with advanced paternal age through the addition of idebenone. Sperm from men aged >40 years and older CBAF1 mice (12–18 months), were treated with 5 µM and 50 µM of idebenone and intracellular and superoxide ROS concentrations assessed. Following in vitro fertilization (IVF), embryo development, blastocyst differentiation, DNA damage and cryosurvival, pregnancy and implantation rates and fetal and placental weights were assessed. Five µM of idebenone given to aged human and mouse sperm reduced superoxide concentrations ~20% (p < 0.05), while both 5 and 50 µM reduced sperm intracellular ROS concentrations in mice ~30% (p < 0.05). Following IVF, 5 µM of idebenone to aged sperm increased fertilization rates (65% vs. 60%, p < 0.05), blastocyst total, trophectoderm and inner cell mass cell numbers (73 vs. 66, 53 vs. 47 and 27 vs. 24, respectively, p < 0.01). Treatment with idebenone also increased blastocyst cryosurvival rates (96% vs. 78%, p < 0.01) and implantation rates following embryo transfer (35% vs. 18%, p < 0.01). Placental weights were smaller (107 mg vs. 138 mg, p < 0.05), resulting in a larger fetal to placental weight ratio (8.3 vs. 6.3, p = 0.07) after sperm idebenone treatment. Increased sperm ROS concentrations associated with advanced paternal age are reduced with the addition of idebenone in vitro, and are associated with improved fertilization rates, embryo quality and implantation rates after IVF.

Idebenone: When an antioxidant is not an antioxidant

Idebenone is a well described drug that was initially developed against dementia. The current literature widely portrays this molecule as a potent antioxidant and CoQ₁₀ analogue. While numerous papers seem to support this view, a closer look indicates that the pharmacokinetics of idebenone do not support these claims. A major discrepancy between achievable tissue levels, especially in target tissues such as the brain, and doses required to show the proposed effects, significantly questions our current understanding. This review explains how this has happened and highlights the discrepancies in the current literature. More importantly, based on some recent discoveries, a new framework is presented that can explain the mode of action of this molecule and can align formerly contradictory results. Finally, this new appreciation of the molecular activities of idebenone provides a rational approach to test idebenone in novel indications that might have not been considered previously for this drug.

Oxygen and nitrite reduction by heme-deficient sulphite oxidase in a patient with mild sulphite oxidase deficiency

Isolated sulphite oxidase deficiency (iSOD) is an autosomal recessive inborn error in metabolism characterised by accumulation of sulphite, which leads to death in early infancy. Sulphite oxidase (SO) is encoded by the SUOX gene and forms a heme- and molybdenum-cofactor-dependent enzyme localised in the intermembrane space of mitochondria. Within SO, both cofactors are embedded in two separated domains, which are linked via a flexible 11 residue tether. The two-electron oxidation of sulphite to sulphate occurs at the molybdenum active site. From there, electrons are transferred via two intramolecular electron transfer steps (IETs) via the heme cofactor and to the physiologic electron acceptor cytochrome c. Previously, we reported nitrite and oxygen to serve as alternative electron acceptors at the Moco active site, thereby overcoming IET within SO. Here, we present evidence for these reactions to occur in an iSOD patient with an unusual mild disease representation. In the patient, a homozygous c.427C>A mutation within the SUOX gene leads to replacement of the highly conserved His143 to Asn. The affected His143 is one of two heme-iron-coordinating residues within SO. We demonstrate, that the H143N SO variant fails to bind heme in vivo leading to the elimination of SO-dependent cytochrome c reduction in mitochondria. We show, that sulphite oxidation at the Moco domain is unaffected in His143Asn SO variant and demonstrate that nitrite and oxygen are able to serve as electron acceptors for sulphite-derived electrons in cellulo. As result, the patient H143N SO variant retains residual sulphite oxidising activity thus ameliorating iSOD progression.

The Mitochondrial Targets of Neuroprotective Drug Vinpocetine on Primary Neuron Cultures, Brain Capillary Endothelial Cells, Synaptosomes, and Brain Mitochondria

Vinpocetine is considered as neuroprotectant drug and used for treatment of brain ischemia and cognitive deficiencies for decades. A number of enzymes, channels and receptors can bind vinpocetine, however the mechanisms of many effects' are still not clear. The present study investigated the effects of vinpocetine from the mitochondrial bioenergetic aspects. In primary brain capillary endothelial cells the purinergic receptor-stimulated mitochondrial Ca²⁺ uptake and efflux were studied. Vinpocetine exerted a partial inhibition on the mitochondrial calcium efflux. In rodent brain synaptosomes vinpocetine (30 μM) inhibited respiration in uncoupler stimulated synaptosomes and decreased H₂O₂ release from the nerve terminals in resting and in complex I inhibited conditions, respectively. In isolated rat brain mitochondria using either complex I or complex II substrates leak respiration was stimulated, but ADP-induced respiration was inhibited by vinpocetine. The stimulation of oxidation was associated with a small extent of membrane depolarization. Mitochondrial H₂O₂ production was inhibited by vinpocetine under all conditions investigated. The most pronounced effects were detected with the complex II substrate succinate. Vinpocetine also mitigated both Ca²⁺-induced mitochondrial Ca²⁺-release and Ca²⁺-induced mitochondrial swelling. It lowered the rate of mitochondrial ATP synthesis, while increasing ATPase activity. These results indicate more than a single mitochondrial target of this vinca alkaloid. The relevance of the affected mitochondrial mechanisms in the anti ischemic effect of vinpocetine is discussed.

Idebenone improves quality of ram sperm by mitigating oxidative stress during cryopreservation

The present study was designed to test the effect of different levels of idebenone, a potent antioxidant on the quality of ram semen at post thaw. Eighteen (18) ejaculates were collected and extended with tris extender supplemented with no antioxidant (CON), with 2 μM idebenone (Id2), 5 μM idebenone (Id5), 7.5 μM idebenone (Id7.5) and 10 μM idebenone (Id10). The sperm quality was determined in terms of percent sperm motility, live sperm percentage, percent hypoosmotic swelling test (HOST) positive spermatozoa and percent intact acrosome (PIA). Moreover, malondialdehyde (MDA) level, an end product of lipid peroxidation (LPO) was also measured at post thaw both in seminal plasma and sperm cell. At post thaw, the percent sperm motility was significantly higher (p < 0.05) for Id10 as compared to Id2, Id5, Id7.5 and control. The live sperm percentage was non-significantly (p > 0.05) higher for Id10 as compared to control, Id5 and Id7.5 but significantly higher than Id2. The percent HOST positive spermatozoa was significantly higher (p < 0.05) for Id10 than control, Id2 and Id5. The MDA level in seminal plasma was significantly lower (p < 0.05) for Id10 than control and Id2. The MDA level in spermatozoa did show similar trend as in seminal plasma. Further, all the sperm parameters at all idebenone levels declined significantly from pre freeze to post thaw. In conclusion, idebenone at 10 μM level improved post thaw sperm quality by mitigating peroxidative stress, hence could be considered as a promising antioxidant additive for cryopreservation of ram semen.

Influence of idebenone on ram semen quality stored at 4°C

The current study was designed to investigate the effect of idebenone (Id), an antioxidant on ram semen quality. Semen samples were collected, pooled and diluted in a Tris-based extender supplemented with 0, 1, 2, 4 and 8 µM idebenone. Computer-assisted sperm analysis was used to evaluate spermatozoa kinematics. Sperm viability and membrane functionality were assessed respectively, by eosin-nigrosin staining and HOS test. Biochemical assays were carried out to measure different metabolites in spermatozoa and medium at 0, 24, 48 and 72 hr. Total and forward progressive motility were greater in 1, 2 and 4 µM idebenone treated groups compared to control at 24, 48 and 72 hr time points (p < 0.05). Semen supplementation with Id significantly increased viability and functionality of spermatozoa membrane during storage (p < 0.05). Lower amounts of lipid hydroperoxides in medium and spermatozoa were observed in Id-treated groups compared to control one at 24 and 48 hr of storage (p < 0.05). Medium and spermatozoa amounts of malondialdehyde and nitric oxide were less in Id 4 µM group compared to the control at 72 hr (p < 0.05). Total antioxidant capacity values and superoxide dismutase activity of spermatozoa and medium were greater in 2 and 4 µM idebenone treated groups in comparison with the control at 72 hr (p < 0.05). Results of the current study indicated that ram semen supplementation with Id at 4 µM level improved quality by ameliorating nitrosative and peroxidative stress, hence could be considered as an antioxidant additive during storage at 4°C.

Idebenone and neuroprotection: antioxidant, pro-oxidant, or electron carrier?

Ubiquinone, commonly called coenzyme Q10 (CoQ), is a lipophilic electron carrier and endogenous antioxidant found in all cellular membranes. In the mitochondrial inner membrane it transfers electrons to complex III of the electron transport chain. The short chain CoQ analogue idebenone is in clinical trials for a number of diseases that exhibit a mitochondrial etiology. Nevertheless, evidence that idebenone ameliorates neurological symptoms in human disease is inconsistent. Although championed as an antioxidant, idebenone can also act as a pro-oxidant by forming an unstable semiquinone at complex I. The antioxidant function of idebenone is critically dependent on two-electron reduction to idebenol without the creation of unstable intermediates. Recently, cytoplasmic

NAD(P)H

quinone oxidoreductase 1 (NQO1) was identified as a major enzyme catalyzing idebenone reduction. While reduction allows idebenone to act as an antioxidant, evidence also suggests that NQO1 enables idebenone to shuttle reducing equivalents from cytoplasmic NAD(P)H to mitochondrial complex III, bypassing any upstream damage to the electron transport chain. In this mini-review we discuss how idebenone can influence mitochondrial function within the context of cytoprotection. Importantly, in the brain NQO1 is expressed primarily by glia rather than neurons. As NQO1 is an inducible enzyme regulated by oxidative stress and the nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway, optimizing NQO1 expression in appropriate cell types within a specific disease context may be key to delivering on idebenone's therapeutic potential.

In vitro cytotoxicity, DNA cleavage and SOD-mimic activity of copper(II) mixed-ligand quinolinonato complexes

Six mixed-ligand copper(II) complexes with the composition [Cu(qui)(L)]BF(4)·xH(2)O (1-6), where Hqui=2-phenyl-3-hydroxy-4(1H)-quinolinone, L=2,2'-bipyridine (bpy) (1), 1,10-phenanthroline (phen) (2), bis(2-pyridyl)amine (ambpy) (3), 5-methyl-1,10-phenanthroline (mphen) (4), 5-nitro-1,10-phenanthroline (nphen) (5) and bathophenanthroline (bphen) (6), were prepared, fully characterized and studied for their in vitro cytotoxicity on human osteosarcoma (HOS) and human breast adenocarcinoma (MCF7) cancer cell lines. The overall promising results of the cytotoxicity were found for all the complexes, while the best results were achieved for complex 6, with IC(50)=2.6 ± 0.8 μM (HOS), and 1.3 ± 0.5 μM (MCF7). The interactions of the Cu(II) complexes 1-6 with calf thymus DNA were investigated by the UV-visible spectral titration. An agarose-gel electrophoretic method of oxidative damage determination to circular plasmid pUC19 was used to assess the ability of the complexes to act as chemical nucleases. A high effectiveness of DNA cleavage was observed for 2, 4 and 5. In vitro antioxidative activity of the complexes was studied by the superoxide dismutase-mimic (SOD-mimic) method. The best result was afforded by complex 1 with IC(50)=4.7 ± 1.0 μM, which corresponds to 10.2% of the native Cu,Zn-SOD enzyme activity. The ability of the tested complexes to interact with sulfur-containing biomolecules (cysteine and reduced glutathione) at physiological levels was proved by electrospray-ionization mass spectrometry (ESI-MS).

Angiopoietin-1 mediates inhibition of hypertension-induced release of angiopoietin-2 from endothelial cells

AIMS

Adequate endothelial cell stimulation is a prerequisite for the adaptive remodelling of macro- and microvessels. A pivotal autocrine mechanism following endothelial cell activation is the release of angiopoietin-2 (Ang-2), which subsequently antagonizes the binding of Ang-1 to the Tie-2 receptor, thus sensitizing the endothelial cells to pro-angiogenic and/or pro-inflammatory stimuli. Based on the observation that hypertension in mice reduces the abundance of Ang-2 stored in arterial endothelial cells, this study was aimed at testing the hypothesis that an increase in wall stress (WS) or stretch-a hallmark of hypertension-is sufficient to release Ang-2 from endothelial cells.

METHODS AND RESULTS

In fact, stretching of isolated perfused mouse arteries or human cultured endothelial cells rapidly elicited an increased release of Ang-2. In the cultured endothelial cells, this was preceded by a transient rise in intracellular free calcium, abrogated through calcium chelation and accompanied by a decrease in Tie-2 phosphorylation. Interestingly, Ang-1 abolished the stretch-induced release of Ang-2 from both cultured and native endothelial cells through inhibiting the stretch-dependent mobilization of intracellular calcium.

CONCLUSION

Collectively, these results indicate that increased WS or stretch facilitates the release of Ang-2 from endothelial cell Weibel-Palade bodies, and that Ang-1 can block this by attenuating the stretch-mediated rise in intracellular calcium.

Idebenone inhibition of glutamate release from rat cerebral cortex nerve endings by suppression of voltage-dependent calcium influx and protein kinase A

The present study was aimed at investigating the effect and the possible mechanism of idebenone on endogenous glutamate release in nerve terminals of rat cerebral cortex (synaptosomes). Idebenone inhibited the release of glutamate that was evoked by exposing synaptosomes to the K(+) channel blocker 4-aminopyridine (4-AP), and this phenomenon was concentration dependent. Inhibition of glutamate release by idebenone was prevented by chelating extracellular Ca(2+), or by the vesicular transporter inhibitor bafilomycin A1, but was insensitive to DL-threo-beta-benzyl-oxyaspartate, a glutamate transporter inhibitor. Idebenone decreased the depolarization-induced increase in the cytosolic free Ca(2+) concentration ([Ca(2+)](C)),whereas it did not alter the resting synaptosomal membrane potential or 4-AP-mediated depolarization. The inhibitory effect of idebenone on evoked glutamate release was prevented by blocking the Ca(v)2.2 (N-type) and Ca(v)2.1 (P/Q-type) channels, but not by blocking intracellular Ca(2+) release or Na(+)/Ca(2+) exchange. Furthermore, the idebenone effect on 4-AP-evoked Ca(2+) influx and glutamate release was completely abolished by the protein kinase A (PKA) inhibitors, H89 and KT5720. On the basis of these results, it was concluded that idebenone inhibits glutamate release from rat cortical synaptosomes and this effect is linked to a decrease in [Ca(2+)](C) contributed by Ca(2+) entry through presynaptic voltage-dependent Ca(2+) channels and to the suppression of PKA signaling cascade.

Nitric oxide pros and cons: The role of L-arginine, a nitric oxide precursor, and idebenone, a coenzyme-Q analogue in ameliorating cerebral hypoxia in rat

Evidence exists that nitric oxide (NO) may mediate both protective and pathological responses during brain hypoxia (HP). Reactive oxygen species have also been implicated in the pathophysiological response of the brain tissues to HP. Therefore, this study investigated whether a NO precursor, l-arginine (l-arg), a free radical scavenger, idebenone (ID), and their combination would reduce neurological injury resulting from hemic hypoxia (HP) in rats. Adult male Wistar albino rats were injected with sodium nitrite (60 mg/kg, s.c.) to establish hemic hypoxia. ID (100 mg kg(-1), i.p.) and/or l-arg (100 mg kg(-1), i.p.) were administrated 24 and 1h prior to sodium nitrite intoxication, respectively. Hypoxia significantly decreased hemoglobin concentration, while significantly increased serum lactate dehydrogenase (LDH), creatine phosphokinase (CPK), total nitrate/nitrite, sialic, and uric acids concentrations. Moreover, brain lipid peroxides were significantly enhanced, while reduced glutathione, l-ascorbic acids, adenosine triphosphate (ATP) contents, and the activities of catalase and superoxide dismutase, were significantly reduced in the brain tissue. Pretreatment with either ID or l-arg altered the majority of the above-mentioned biochemical changes in hypoxic rats. Additionally, the combination of these two agents significantly reduced injury marker enzyme activities as well as serum sialic, and uric acids level (P>0.05 vs. control). Moreover, this combination exerted a synergistic antioxidant effect by blocking the induction of lipid peroxidation, preserving brain energy (ATP) content, and greatly reducing the hypoxic alterations in brain enzymatic and non-enzymatic antioxidants. Histopathological examination of the brain tissue supported these biochemical findings. This study showed that ID and l-arg were capable of reducing neurological injury following HP in rat, and support the idea of the usefulness of l-arg and ID as prophylaxis from hypoxic brain injury.

Oxidative stress in the progression of Alzheimer disease in the frontal cortex

We investigated oxidative stress in human postmortem frontal cortexfrom individuals characterized as mild cognitive impairment (n= 8), mild/moderate Alzheimer disease (n = 4), and late-stage Alzheimer disease (n = 9). Samples from subjects with no cognitive impairment (n = 10) that were age- and postmortem interval-matched with these cases were used as controls. The short postmortem intervalbrain samples were processed for postmitochondrial supernatant, nonsynaptic mitochondria, and synaptosome fractions. Samples were analyzed for several antioxidants (glutathione, glutathione peroxidase, glutathione reductase, glutathione-S-transferase, glucose-6-phosphate dehydrogenase, superoxide dismutase, catalase) and the oxidative marker, thiobarbituric acid reactive substances. The tissue was also analyzed for possible changes in protein damage using neurochemical markers for protein carbonyls, 3-nitrotyrosine, 4-hydroxynonenal, andacrolein. All 3 neuropil fractions (postmitochondrial supernatant, mitochondrial, and synaptosomal) demonstrated significant disease-dependent increases in oxidative markers. The highest changes were observed in the synaptosomal fraction. Both mitochondrial and synaptosomal fractions had significant declines in antioxidants (glutathione, glutathione peroxidase, glutathione-S-transferase, and superoxide dismutase). Levels of oxidative markers significantly correlated with Mini-Mental Status Examination scores. Oxidative stress was more localized to the synapses, with levels increasing in a disease-dependent fashion. These correlations implicate an involvement of oxidative stress in Alzheimer disease-related synaptic loss.

Preparation of pH-sensitive liposomes retaining SOD mimic and their anticancer effect

We prepared an anticancer drug based on a pH-sensitive liposome retaining Fe-porphyrin as an SOD mimic. The liposomes contained cationic/anionic lipid combinations and were composed of Fe-porphyrin, 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine, dimethylditetradecylammonium bromide, sodium oleate, and Tween-80. The Fe-porphyrin was released from the liposome at low pH, and the cytotoxicity for cancer cells by the liposome depended on the acidic environments of the endosomes in the cells. Furthermore, although the liposome exhibited an excellent anticancer effect on a gastric cancer cell line, the SOD activity of Fe-porphyrin was shown to have a significant influence on the cytotoxicity toward cancer cells. These findings suggest that the pH-sensitive liposome retaining the Fe-porphyrin as an SOD mimic promises to be a novel anticancer drug for endosomal escape.

Oxidative stress and glaucoma: injury in the anterior segment of the eye

The perturbation of the pro-oxidant/antioxidant balance can lead to increased oxidative damage, especially when the first line of antioxidant defense weakens with age. Chronic changes in the composition of factors present in aqueous or vitreous humor may induce alterations both in trabecular cells and in cells of the optic nerve head. Free radicals and reactive oxygen species are able to affect the cellularity of the human trabecular meshwork (HTM). These findings suggest that intraocular pressure increase, which characterizes most glaucomas, is related to oxidative and degenerative processes affecting the HTM and, more specifically, its endothelial cells. This supports the theory that glaucomatous damage is the pathophysiological consequence of oxidative stress. Glaucomatous subjects might have a genetic predisposition, rendering them more susceptible to reactive oxygen species-induced damage. It is likely that specific genetic factors contribute to both the elevation of IOP and susceptibility of the optic nerve/retinal ganglion cells (RGCs) to degeneration. Thus, oxidative stress plays a fundamental role during the arising of glaucoma-associated lesions, first in the HTM and then, when the balance between nitric oxide and endothelins is broken, in neuronal cell. Vascular damage and hypoxia, often associated with glaucoma, lead to apoptosis of RGCs and may also contribute to the induction of oxidative damage to the HTM. On the whole, these findings support the hypothesis that oxidative damage is an important step in the pathogenesis of primary open-angle glaucoma and might be a relevant target for both prevention and therapy.

Glaucomatous outflow pathway and oxidative stress

Oxidative free radicals and reactive oxygen species (ROS) are able to affect the cellularity of the human trabecular meshwork (HTM). These findings suggest that intraocular pressure increase, which characterises most glaucomas, is related to oxidative degenerative processes affecting the HTM and specifically its endothelial cells. Much evidence indicates that in this region ROS play a fundamental pathogenic role by reducing local antioxidant activities, inducing outflow resistance and exacerbating the activities of superoxide dismutase and glutathione peroxidase in glaucomatous eyes. Furthermore, hydrogen peroxide induces rearrangement of HTM cells and compromises their integrity. Glaucomatous subjects might have a genetic predisposition rendering them more susceptible to ROS-induced damage. A fairly significant correlation between oxidative DNA damage in the HTM and intraocular pressure increase and visual field defects in glaucomatous patients has been demonstrated. Thus, oxidative stress may play a significant role during glaucoma course initially damaging HTM cells, then contributing to the alteration of the homeostasis between NO and endothelins, and finally through its possible involvement in ganglional cell death. On the whole, these findings support the hypothesis that oxidative damage is an important step in the pathogenesis of primary open-angle glaucoma, and might be a relevant target for both prevention and therapy.

Superoxide dismutase as a target enzyme for Fe-porphyrin-induced cell death

The cell viability of human cancer cell lines treated with [5,10-bis(N-methyl-4-pyridyl)-15,20-diphenyl]porphinatoiron(III) (cis-FeMPy(2)P(2)P) has been estimated. The cis-FeMPy(2)P(2)P is a superoxide dismutase (SOD) mimic in vitro that exhibited a significant toxicity in cancer cell lines. This toxicity is rather due to pro-oxidant properties of the iron-porphyrin in vivo. We have demonstrated that there was the relationship between the LD(50) values calculated from the viability of cancer cell lines treated with cis-FeMPy(2)P(2)P and the SOD activities of the cell lines. Furthermore, the inhibition of SOD by antisense S-oligonucleotide increased the cytotoxic effect of cis-FeMPy(2)P(2)P against cancer cells. These results suggest that SOD is a target enzyme for the cell death induced by cis-FeMPy(2)P(2)P as a new class of anticancer agents.

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.

Mitochondria-derived oxidative stress induces a heat shock protein response

In addition to minimizing native and non-native protein aggregations, heat shock proteins (HSPs) regulate programmed cell death pathways. Members of this conserved protein family are in general activated by oxidative stress, and likely help maintain viability under this stress condition. To further our understanding of heat shock protein physiology, we studied whether a specific subtype of oxidative stress, namely that arising from mitochondrial electron transport chain inhibition, induced a heat shock protein response. We exposed human teratocarcinoma (NT2) cells to varying concentrations of the cytochrome oxidase inhibitor sodium azide. Micromolar exposures resulted in a cytoplasm to nucleus translocation of the inducible Hsp70 and of Hsp40, and this was followed by an overall upregulation. The response did not coincide temporally with the onset of azide exposure, but rather was activated when the degree of cytochrome oxidase inhibition (which was progressive over time) surpassed a threshold. Azide did not affect either Hsp70 or Hsp40 dynamics in NT2 rho0 cells, which lack functional electron transport chains. For the azide-exposed native cell line, addition of the antioxidant trolox to the medium abrogated both Hsp70/Hsp40 translocation and upregulation. We conclude that mitochondrial electron transport chain dysfunction activates a heat shock protein response, and that this response is mediated by oxidative stress.

Functional dichotomy: glutathione and vitamin E in homeostasis relevant to primary open-angle glaucoma

Primary open-angle glaucoma (POAG) is a complex chronic neurological disease that can result in blindness. The goal of understanding the aetiology of POAG is to be able to target effective treatment to individuals who will eventually go blind without it. Epidemiological studies of POAG have not specifically addressed the possibility that nutrition may play a role in the development of POAG. A handful of papers have considered that nutrition may have an impact on POAG patients. POAG is not believed to be a 'vitamin-deficiency disease'. The concept of 'vitamin-deficiency diseases' and the recommended daily allowances have not kept pace with the growing understanding of the cellular and molecular functions of vitamins and other micronutrients. The aetiology of POAG remains a mystery. Discoveries in cell physiology can be assimilated from the literature and applied to known homeostatic mechanisms of the eye. In this way the possible roles of nutritional components involved in the aetiology of POAG can be described. The mechanisms may be subject to many influences in ways that have yet to be defined. Two distinct changes in the trabecular meshwork can be identified: trabecular meshwork changes that cause intra-ocular pressure to increase and trabecular meshwork changes that are directly correlated to optic nerve atrophy. Compelling evidence suggests that collagen trabecular meshwork extracellular matrix (ECM) remodelling is correlated to increased intraocular pressure in POAG. Elastin trabecular meshwork ECM remodelling is correlated to POAG optic nerve atrophy. There appear to be two different pathways of ECM remodelling and apoptosis induction in POAG. The pathway for collagen remodelling and apoptosis induction seems to be exogenously influenced by water-soluble antioxidants, for example, glutathione. The pathway for elastin remodelling and apoptosis induction seems to be influenced by endogenous lipid-soluble antioxidants, for example, vitamin E. Roles can be defined for antioxidants in the two different pathways of ECM remodelling and apoptosis induction. This suggests that antioxidants are important in maintaining cellular homeostasis relevant to the aetiology of POAG.

Antioxidant defence of the neonatal rat brain against acute hyperammonemia

Oxidative stress associated with the presence of elevated concentrations of ammonia in the brain has been proposed as one possible mechanism involved in ammonia toxicity. In a previous study [Brain Res.973 (2003) 31], we reported that neonatal rats are more resistant to acute ammonia toxicity than adult rats. In the present work, we studied the antioxidant status of the brain in hyperammonemic neonatal rats. Increased activities of the antioxidant enzymes and enhanced glutathione content were found in the brains of the hyperammonemic neonatal rats as compared to the controls. In addition, no changes in brain reactive oxygen species (ROS) levels and lipid peroxidation due to hyperammonemia were found. Therefore, acute ammonia intoxication does not induce oxidative stress in neonatal rats, a fact that may explain the resistance against hyperammonemia shown by neonatal rats.

Cytosolic and mitochondrial ROS in staurosporine-induced retinal cell apoptosis

In this study, we investigated the involvement of reactive oxygen species (ROS) and calcium in staurosporine (STS)-induced apoptosis in cultured retinal neurons, under conditions of maintained membrane integrity. The antioxidants idebenone (IDB), glutathione-ethylester (GSH/EE), trolox, and Mn(III)tetrakis (4-benzoic acid) porphyrin chloride (MnTBAP) significantly reduced STS-induced caspase-3-like activity and intracellular ROS generation. Endogenous sources of ROS production were investigated by testing the effect of the following inhibitors: 7-nitroindazole (7-NI), a specific inhibitor of the neuronal isoform of nitric oxide synthase (nNOS); arachidonyl trifluoromethyl ketone (AACOCF(3)), a phospholipase A(2) (PLA(2)) inhibitor; allopurinol, a xanthine oxidase inhibitor; and the mitochondrial inhibitors rotenone and oligomycin. All these compounds decreased caspase-3-like activity and ROS generation, showing that both mitochondrial and cytosolic sources of ROS are implicated in this mechanism. STS induced a significant increase in intracellular calcium concentration ([Ca(2+)](i)), which was partially prevented in the presence of IDB and GSH/EE, indicating its dependence on ROS generation. These two antioxidants and the inhibitors allopurinol and 7-NI also reduced the number of TdT-mediated dUTP nick-end labeling-positive cells. Thus, endogenous ROS generation and the rise in intracellular calcium are important inter-players in STS-triggered apoptosis. Furthermore, the antioxidants may help to prolong retinal cell survival upon apoptotic cell death.

Selective cell death by water-soluble Fe-porphyrins with superoxide dismutase (SOD) activity

We investigated the effect on cell death of reactive oxygen species induced by [[5,10 (or 5,15)-bis(N-methyl-4-pyridyl)-15,20 (or 10,20) diphenyl]porphinato]iron (cis-FeMPy(2)P(2)P or trans-FeMPy(2)P(2)P) with SOD activity. The SOD activities of the cis-FeMPy(2)P(2)P and trans-FeMPy(2)P(2)P were measured using stopped-flow kinetic analysis. The cell viability of four cell lines treated with cis-Fe-porphyrin, trans-Fe-porphyrin, mitomycin c (MMC), or cisplatin was estimated by the alamar blue exclusion assay of the modified MTT method. The amount of cis-FeMPy(2)P(2)P and trans-FeMPy(2)P(2)P in the Walker 256 cultured for 24 h was 4.0 and 2.6 fmolcell(-1), respectively, indicating that the plasma membrane permeability of the Fe-porphyrins depended on their structure. Cis-FeMPy(2)P(2)P selectively killed Walker 256 and H-4-II-E as cancer cells but not FR and BRL-3A as normal cells and showed a significant cytotoxicity for the cancer cells compared with trans-FeMPy(2)P(2)P, MMC and cisplatin. We believe that cis-FeMPy(2)P(2)P as an SOD mimic converts intracellular O(2)(*-) to H(2)O(2) and that H(2)O(2) or *OH causes DNA damage and induces cell death. This result suggests that for the SOD mimic, O(2)(*-) may be useful as a target molecule to induce selective cell death between cancer and normal cells and that a metalloporphyrin having SOD activity is a new class of anticancer agents.

Methamphetamine selectively alters brain glutathione

As methamphetamine-induced neurotoxicity has been proposed to involve oxidative stress, reduced and oxidized glutathione (GSH and GSSG, respectively), vitamin E and ascorbate were measured in the striata of rats killed 2 or 24 h after a neurotoxic regimen of methamphetamine. At 2 h, methamphetamine increased GSH and GSSG (32. 5% and 43.7%, respectively) compared to controls at 2 h. No difference was seen in glutathione at 24 h, and in vitamin E and ascorbate at either time point. These findings indicate selectivity of methamphetamine for the glutathione system and a role for methamphetamine in inducing oxidative stress.

Oxidative glutamate toxicity involves mitochondrial dysfunction and perturbation of intracellular Ca2+ homeostasis

Glutamate toxicity on PC12 cells is mediated by oxidative stress as a consequence of the inhibition of a cystine uptake system with depletion of GSH. In this study we report that glutamate decreases PC12 cell viability, inhibiting the reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). This decrease was prevented by the antioxidants vitamin E, idebenone and L-deprenyl, which were also shown to be effective in reducing the accumulation of reactive oxygen species (ROS) in cells exposed to glutamate, decreasing the fluorescence of 2',7'-dichlorofluorescein (DCF). Incubation of PC12 cells with high glutamate concentrations induced mitochondrial dysfunction, leading to the loss of mitochondrial transmembrane potential, evaluated as a decrease in rhodamine 123 (Rh123) retention by mitochondria, and to the decrease of intracellular ATP levels. The mitochondrial dysfunction, induced by glutamate, can be involved in the observed increase of [Ca2+]i. The elevation of [Ca2+]i occurred after GSH depletion, suggesting that oxidative stress is involved in the disturbances of intracellular calcium homeostasis. In conclusion, our data indicate that glutamate, at concentrations which block cystine uptake in PC12 cells leading to GSH depletion and inducing oxidative stress, increases ROS accumulation and decreases cell survival by a mechanism involving mitochondrial dysfunction and impairment of Ca2+ homeostasis.

Uptake of lipoprotein-associated alpha-tocopherol by primary porcine brain capillary endothelial cells

From the severe neurological syndromes resulting from vitamin E deficiency, it is evident that an adequate supply of the brain with alpha-tocopherol (alphaTocH), the biologically most active member of the vitamin E family, is of utmost importance. However, uptake mechanisms of alphaTocH in cells constituting the blood-brain barrier are obscure. Therefore, we studied the interaction of low (LDL) and high (HDL) density lipoproteins (the major carriers of alphaTocH in the circulation) with monolayers of primary porcine brain capillary endothelial cells (pBCECs) and compared the ability of these two lipoprotein classes to transfer lipoprotein-associated alphaTocH to pBCECs. With regard to potential binding proteins, we could identify the presence of the LDL receptor and a putative HDL3 binding protein with an apparent molecular mass of 100 kDa. At 4 degrees C, pBCECs bound LDL with high affinity (K(D) = 6 nM) and apolipoprotein E-free HDL3 with low affinity (98 nM). The binding capacity was 20,000 (LDL) and 200,000 (HDL3) lipoprotein particles per cell. alphaTocH uptake was approximately threefold higher from HDL3 than from LDL when [14C]alphaTocH-labeled lipoprotein preparations were used. The majority of HDL3-associated alphaTocH was taken up in a lipoprotein particle-independent manner, exceeding HDL3 holoparticle uptake 8- to 20-fold. This uptake route is less important for LDL-associated alphaTocH (alphaTocH uptake approximately 1.5-fold higher than holoparticle uptake). In line with tracer experiments, mass transfer studies with unlabeled lipoproteins revealed that alphaTocH uptake from HDL3 was almost fivefold more efficient than from LDL. Biodiscrimination studies indicated that uptake efficacy for the eight different stereoisomers of synthetic alphaTocH is nearly identical. Our findings indicate that HDL could play a major role in supplying the central nervous system with alphaTocH in vivo.

Synaptosomal response to oxidative stress: effect of vinpocetine

It has been suggested that reactive oxygen species (ROS) play a role in the neuronal damage occurring in ischemic injury and neurodegenerative disorders and that their neutralization by antioxidant drugs may delay or minimize neurodegeneration. In the present study we examine whether vinpocetine can act as an antioxidant and prevent the formation of ROS and lipid peroxidation in rat brain synaptosomes. After ascorbate/Fe2+ treatment a significant increase in oxygen consumption (about 5-fold) and thiobarbituric acid reactive substances (TBARS) formation (about 7-fold) occurred as compared to control conditions. Vinpocetine inhibited the ascorbate/Fe2+ stimulated consumption of oxygen and TBARS accumulation, an indicator of lipid peroxidation, in a concentration-dependent manner. The ROS formation was also prevented by vinpocetine. Oxidative stress increased significantly the fluorescence of the probes 2',7'-dichlorodihydrofluorescein (DCFH2-DA) (about 6-fold) and dihydrorhodamine (DHR) 123 (about 10-fold), which is indicative of intrasynaptosomal ROS generation. Vinpocetine at 100 microM concentration decreased the fluorescence of DCFH2-DA and DHR 123 by about 50% and 83%, respectively. We conclude that the antioxidant effect of vinpocetine might contribute to the protective role exerted by the drug in reducing neuronal damage in pathological situations.

Fumonisin B1-induced DNA damage in rat liver and spleen: effects of pretreatment with coenzyme Q10, L-carnitine, alpha-tocopherol and selenium

Active oxygen radical species are reported to cause organ damage. This study was designed to determine whether oxidative stress contributed to the initiation or progression of hepatic and splenic cell DNA damage induced by fumonisin B1 (FB1) in rats. Another aim was to investigate the protective effects of the antioxidants coenzyme Q10 (CoQ10), L-carnitine, vitamin E (alpha-tocopherol) and selenium against DNA damage in the liver and spleen of rats treated with FB1. Fasted rats were injected intravenously with a single dose of fumonisin B1 at 1.55 mg kg-1 body wt. into the tail vein. Treatment with FB1 led to splenic and hepatic DNA fragmentation in 85% of the test animals. DNA fragmentation was investigated as a critical event in toxic cell death by testing total Ca2+ in liver. FB1 administration caused total Ca2+ in liver to increase within 4 h (204% of control). Measurement of liver enzyme activities showed an increase in aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT). FB1 also markedly decreased splenic and hepatic glutathione (GSH) levels. Pretreatment with CoQ10 (30 mg CoQ10 kg-1 diet) together with L-carnitine (2.8 mg carnitine kg-1 diet), alpha-tocopherol (30 IU vitamin E kg-1 diet) and selenium (1 mg selenium as sodium selenite kg-1 diet), decreased DNA damage and the activities of Ca2+, ASAT and ALAT in the liver. On the other hand, the level of GSH was slightly increased. The CoQ10 alone did not significantly protect against toxic cell death and glutathione depletion caused by FB1. Oxidative damage caused by FB1 may be one of the underlining mechanisms of FB1-induced cell injury and DNA damage.