Oxidative Stress-related Neurodegenerative Disorders Research Articles

Isolation of a novel isoprenylated phenolic compound and neuroprotective evaluation of Dodonaea viscosa extract against cerebral ischaemia–reperfusion injury in rats

Dodonaea viscosa grows widely in Saudi Arabia, but studies evaluating its neuroprotective activity are lacking. Thus, this study aimed to isolate and identify the secondary metabolites and evaluate the neuroprotective effects of D. viscosa leaves. The isolation and identification of phytochemicals were performed using chromatographic and spectroscopic techniques. The neuroprotective potential of the extract was evaluated against focal cerebral ischaemia–reperfusion injury in rat model. Neurobehavioural deficits in the rats were evaluated, and their brains were harvested to measure infarct volume and oxidative biomarkers. Results revealed the presence of three compounds: a novel isoprenylated phenolic derivative that was elucidated as 4-hydroxy-3-(3ʹ-methyl-2ʹ-butenyl) phenyl 1-O-β-D-apiosyl-(1ʹʹʹ → 6ʹʹ)- β-D-glucopyranoside (named Viscomarfadol) and two known compounds (isorhamnetin-3-O-rutinoside and epicatechin (4–8) catechin). Pre-treatment of the rats with the extract improved neurological outcomes. It significantly reduced neurological deficits and infarct volume; significantly reduced lipid peroxidation, as evidenced by decreased malondialdehyde levels; and significantly elevated antioxidant (superoxide dismutase, catalase, and glutathione) activities. These results indicate that D. viscosa is a promising source of bioactive compounds that can improve neurological status, decrease infarct volume, and enhance antioxidant activities in rats with cerebral ischaemic injury. Thus, D. viscosa could be developed into an adjuvant therapy for ischaemic stroke and other oxidative stress-related neurodegenerative disorders. Further investigations are warranted to explore other bioactive compounds in D. viscosa and evaluate their potential neuroprotective activities.

Cysteine Donor-Based Brain-Targeting Prodrug: Opportunities and Challenges.

Overcoming blood-brain barrier (BBB) to improve brain bioavailability of therapeutic drug remains an ongoing concern. Prodrug is one of the most reliable approaches for delivering agents with low-level BBB permeability into the brain. The well-known antioxidant capacities of cysteine (Cys) and its vital role in glutathione (GSH) synthesis indicate that Cys-based prodrug could potentiate therapeutic drugs against oxidative stress-related neurodegenerative disorders. Moreover, prodrug with Cys moiety could be recognized by the excitatory amino acid transporter 3 (EAAT3) that is highly expressed at the BBB and transports drug into the brain. In this review, we summarized the strategies of crossing BBB, properties of EAAT3 and its natural substrates, Cys and its donors, and Cys donor-based brain-targeting prodrugs by referring to recent investigations. Moreover, the challenges that we are faced with and future research orientations were also addressed and proposed. It is hoped that present review will provide evidence for the pursuit of novel Cys donor-based brain-targeting prodrug.

Emodin ameliorates antioxidant capacity and exerts neuroprotective effect via PKM2-mediated Nrf2 transactivation

Pyruvate kinase M2 (PKM2) is overexpressed in neuronal cells. However, there are few studies on the involvement of PKM2 modulators in neurodegenerative diseases. Emodin, a dominating anthraquinone derivative extracting from the rhizome of rhubarb, has received expanding consideration due to its pharmacological properties. Our data reveal that emodin could resist hydrogen peroxide- or 6-hydroxydopamine-mediated mitochondrial fission and apoptosis in PC12 cells (a neuron-like rat pheochromocytoma cell line). Notably, emodin at nontoxic concentrations significantly inhibits PKM2 activity and promotes dissociation of tetrameric PKM2 into dimers in cells. The PKM2 dimerization enhances the interaction of PKM2 and NFE2-related factor 2 (Nrf2), which further triggers the activation of the Nrf2/ARE pathway to upregulate a panel of cytoprotective genes. Modulating the PKM2/Nrf2/ARE axis by emodin unveils a novel mechanism for understanding the pharmacological functions of emodin. Our findings indicate that emodin is a potential candidate for the treatment of oxidative stress-related neurodegenerative disorders.

Expression of PON2 isoforms varies among brain regions in male and female African green monkeys

Mitochondrial dysfunction and oxidative stress contribute to the neuropathology of neurodegenerative disorders such as Parkinson's disease (PD). Paraoxonase-2 (PON2) is a mitochondrial protein that mitigates oxidative stress, enhances mitochondrial function and exhibits anti-inflammatory properties. Previously, we have documented sex-based variation in PON2 with higher brain PON2 expression in female (2-fold) as compared to male African green monkeys. This aim of this study is to identify PON2 isoforms and explore the region-based variations in the protein level of PON2 in brain of African green monkeys. Male and female brain tissue samples (striatum, hippocampus, occipital cortex, dorsolateral prefrontal cortex) from African green monkeys (Chlorocebus sabaeus) were analyzed by western blotting technique for PON2 expression. We found two PON2 isoforms (39 and 41 kDa) in each examined brain region of male and female monkeys. Male monkeys showed no significant difference in the expression level of PON2 isoforms among different brain regions whereas female monkeys showed a significant difference in the expression level of PON2 isoforms in all examined regions except dorsolateral prefrontal cortex. In addition, the result revealed highest expression of PON2 protein in striatum compared to other brain regions in both male and female monkeys. This report is the first to quantify expression of PON2 isoforms in different brain regions and it also establishes the existence of sex as well as region-based variation in PON2 protein expression in primate brain. Since PON2 serves a protective role for dopaminergic neurons it should be considered as a druggable target for oxidative stress-related neurodegenerative disorders like PD. We anticipate that the outcome of this study will contribute to the development of neuroprotective strategies in PD.

Effect of Vasicinone against Paraquat-Induced MAPK/p53-Mediated Apoptosis via the IGF-1R/PI3K/AKT Pathway in a Parkinson’s Disease-Associated SH-SY5Y Cell Model

Vasicinone is a quinazoline alkaloid isolated from the Adhatoda vasica plant. In this study, we explored the neuroprotective effect and underlying molecular mechanism of vasicinone against paraquat-induced cellular apoptosis in SH-SY5Y cells. Vasicinone reduced the paraquat-induced loss of cell viability, rescued terminal deoxynucleotide transferase-mediated dUTP nick end-labeling (TUNEL)-positive apoptotic nuclei, and suppressed generation of reactive oxygen species (ROS) in a dose-dependent manner. Western blotting analysis revealed that vasicinone increased the phosphorylation of IGF1R/PI3K/AKT cell survival signaling molecules and downregulated the paraquat-induced, mitogen-activated protein kinase (MAPK)/c-Jun N-terminal kinase (JNK)-mediated apoptotic pathways compared to that observed in cells not treated with vasicinone. This protection depended critically on the activation of IGF1R, and the silencing of IGF1R by siRNA completely abrogated the protective effect of vasicinone in SH-SY5Y cells. Our findings indicated that vasicinone is a potential candidate for the treatment of Parkinson’s disease and possibly other oxidative stress-related neurodegenerative disorders.

Neuroprotective effect of quercetin in murine cortical brain tissue cultures

•This Novel Brain slice culture described here proved to be useful for the study of therapeutic potential of various drugs.•Quercetin has shown to ameliorate the induced oxidative stress to brain Tissues specially neurons in-vitro.•Supplementation with Quercetin could potentially use as therapy for neurodegenerative disorder. PurposeQuercetin (QR) is bioflavonoids known for its antioxidants property and its ability to alleviate oxidative stress and promote cellular survival. The aim of this study was to explore the neuroprotective potential of QR against the induced oxidative stress.MethodsCortical brain tissue cultures from one week old Wister rats were set up in four groups. Group 1: the control group without any treatments; Group 2: cortical cultures treated with 1 mM H2O2 for one hour; Group 3: Cortical cultures pretreated with varying doses of QR for 24 h followed by treatment with 1 mM H2O2 for 1 h; Group 4: Cortical cultures treated with the vehicle alone (DMSO). The cortical Tissues from all four groups were homogenized, both the homogenized cortical tissues and conditioned medium was used for the biochemical assay. For histology studies cortical brain tissue were fixed in 10% formalin and stained with H&E.ResultsPretreatment with 100 μg/ml showed the optimum concentration, which completely ameliorates the effect of induced oxidative stress by H2O2. All of the biochemical markers of oxidative stress such as lipid peroxidation, GST enzyme assay, DNA damage and fragmentation were completely reversed with the pretreatments of QR. Histology of the cortical tissues further confirmed the biochemical assays as it showed the pretreatments with QR resulted in the neuronal survival and viability.ConclusionsThis study further reiterated the neuroprotective role of QR against oxidative stress-related neurodegenerative disorders. Quercetin (QR) is bioflavonoids known for its antioxidants property and its ability to alleviate oxidative stress and promote cellular survival. The aim of this study was to explore the neuroprotective potential of QR against the induced oxidative stress. Cortical brain tissue cultures from one week old Wister rats were set up in four groups. Group 1: the control group without any treatments; Group 2: cortical cultures treated with 1 mM H2O2 for one hour; Group 3: Cortical cultures pretreated with varying doses of QR for 24 h followed by treatment with 1 mM H2O2 for 1 h; Group 4: Cortical cultures treated with the vehicle alone (DMSO). The cortical Tissues from all four groups were homogenized, both the homogenized cortical tissues and conditioned medium was used for the biochemical assay. For histology studies cortical brain tissue were fixed in 10% formalin and stained with H&E. Pretreatment with 100 μg/ml showed the optimum concentration, which completely ameliorates the effect of induced oxidative stress by H2O2. All of the biochemical markers of oxidative stress such as lipid peroxidation, GST enzyme assay, DNA damage and fragmentation were completely reversed with the pretreatments of QR. Histology of the cortical tissues further confirmed the biochemical assays as it showed the pretreatments with QR resulted in the neuronal survival and viability. This study further reiterated the neuroprotective role of QR against oxidative stress-related neurodegenerative disorders.

Honokiol Alleviates Oxidative Stress-Induced Neurotoxicity via Activation of Nrf2.

Honokiol (Hon), a polyphenol and main active ingredient from the bark of Magnolia officinalis, has been documented as having multiple pharmacological functions, including neuroprotection. However, the mechanisms underlying its neuroprotective effects are not well-defined. In this study, we reported that Hon attenuates the H2O2- or 6-hydroxydopamine (6-OHDA)-induced apoptosis of PC12 cells by increasing the glutathione level and upregulating a multitude of cytoprotective proteins, including heme oxygenase 1, NAD(P)H:quinone oxidoreductase 1, thioredoxin 1, and thioredoxin reductase 1. Further studies reveal that Hon promotes transcription factor Nrf2 nuclear translocation and activation. Moreover, the cytoprotection of Hon was antagonized by silence of Nrf2 expression, highlighting the fact that Nrf2 is critically engaged in the cellular functions of Hon. Taken together, our study identified that Hon is an effective agonist of Nrf2 in the neuronal system and displays potent neuroprotection against oxidative stress-mediated PC12 cell damage. These findings indicate that Hon is promising for further development as a therapeutic drug against oxidative stress-related neurodegenerative disorders.

Melatonin Attenuates Oxidative Damage Induced by Acrylamide In Vitro and In Vivo.

Acrylamide (ACR) has been classified as a neurotoxic agent in animals and humans. Melatonin (MT) has been shown to be potentially effective in preventing oxidative stress related neurodegenerative disorders. In this study, whether MT exerted a protective effect against ACR-induced oxidative damage was investigated. Results in cells showed that reactive oxygen species (ROS) and malondialdehyde (MDA) significantly increased after ACR treatment for 24 h. MT preconditioning or cotreatment with ACR reduced ROS and MDA products, whereas the inhibitory effect of MT on oxidant generation was attenuated by blocking the MT receptor. Increased DNA fragmentation caused by ACR was significantly decreased by MT coadministration. In vivo, rats at 40 mg/kg/day ACR by gavage for 12 days showed weight loss and gait abnormality, Purkinje cell nuclear condensation, and DNA damage in rat cerebellum. MT (i.p) cotreatment with ACR not only recovered weight and gait of rats, but also decreased nuclear condensation and DNA damage in rat cerebellum. Using MDA generation, glutathione (GSH) level, superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) activities in rat cerebellum as indicators, MT alleviated ACR-induced lipid peroxidation and depressed antioxidant capacity. Our results suggest that MT effectively prevents oxidative damage induced by ACR.

Edible bird's nest ameliorates oxidative stress-induced apoptosis in SH-SY5Y human neuroblastoma cells.

BackgroundParkinson’s disease (PD) is the second most common neurodegenerative disorder affecting the senile population with manifestation of motor disability and cognitive impairment. Reactive oxygen species (ROS) is implicated in the progression of oxidative stress-related apoptosis and cell death of the midbrain dopaminergic neurons. Its interplay with mitochondrial functionality constitutes an important aspect of neuronal survival in the perspective of PD. Edible bird’s nest (EBN) is an animal-derived natural food product made of saliva secreted by swiftlets from the Aerodamus genus. It contains bioactive compounds which might confer neuroprotective effects to the neurons. Hence this study aims to investigate the neuroprotective effect of EBN extracts in the neurotoxin-induced in vitro PD model.MethodsEBN was first prepared into pancreatin-digested crude extract and water extract. In vitro PD model was generated by exposing SH-SY5Y cells to neurotoxin 6-hydroxydopamine (6-OHDA). Cytotoxicity of the extracts on SH-SY5Y cells was tested using MTT assay. Then, microscopic morphological and nuclear examination, cell viability test and ROS assay were performed to assess the protective effect of EBN extracts against 6-OHDA-induced cellular injury. Apoptotic event was later analysed with Annexin V-propidium iodide flow cytometry. To understand whether the mechanism underlying the neuroprotective effect of EBN was mediated via mitochondrial or caspase-dependent pathway, mitochondrial membrane potential (MMP) measurement and caspase-3 quantification were carried out.ResultsCytotoxicity results showed that crude EBN extract did not cause SH-SY5Y cell death at concentrations up to 75 μg/ml while the maximum non-toxic dose (MNTD) of water extract was double of that of crude extract. Morphological observation and nuclear staining suggested that EBN treatment reduced the level of 6-OHDA-induced apoptotic changes in SH-SY5Y cells. MTT study further confirmed that cell viability was better improved with crude EBN extract. However, water extract exhibited higher efficacy in ameliorating ROS build up, early apoptotic membrane phosphatidylserine externalization as well as inhibition of caspase-3 cleavage. None of the EBN treatment had any effect on MMP.ConclusionsCurrent findings suggest that EBN extracts might confer neuroprotective effect against 6-OHDA-induced degeneration of dopaminergic neurons, particularly through inhibition of apoptosis. Thus EBN may be a viable nutraceutical option to protect against oxidative stress-related neurodegenerative disorders such as PD.

Baicalein protects the brain against neuron impairments induced by MPTP in C57BL/6 mice

Many studies of Parkinson's disease suggest that oxidative stress is involved in the neurodegenerative process. Baicalein has been shown to have antioxidant effects. The present study examines the effect of baicalein on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity in C57BL/6 mice. MPTP treatment impaired spontaneous motor activity and rotarod performance, but baicalein improved this deficit. Moreover, baicalein at 280 and 560mg/kg exhibited a protective effect against the MPTP-induced decrease in tyrosine hydroxylase (TH)-positive fibers in the substantia nigra, demonstrated by the immunohistological, morphological and behavioral outcomes. MPTP treatment also decreased dopamine levels in the striatum. However, treatment with baicalein attenuated these decreases in dopamine levels by changing dopamine catabolism and inhibiting dopamine turnover. The neuroprotective effect of baicalein on dopaminergic neurons may partly be due to its antioxidant properties. Therefore, we speculate that baicalein might be a promising candidate for prevention or treatment of oxidative stress-related neurodegenerative disorders such as Parkinson's disease.

Neuronal effects of 4- t-Butylcatechol: A model for catechol-containing antioxidants

Many herbal medicines and dietary supplements sold as aids to improve memory or treat neurodegenerative diseases or have other favorable effects on the CNS contain a catechol or similar 1,2-dihydroxy aromatic moiety in their structure. As an approach to isolate and examine the neuroprotective properties of catechols, a simple catechol 4- t-Butylcatechol (TBC) has been used as a model. In this study, we investigated the effects of TBC on lipopolysaccharide (LPS)-activated microglial-induced neurotoxicity by using the in vitro model of coculture murine microglial-like cell line HAPI with the neuronal-like human neuroblastoma cell line SH-SY5Y. We also examined the effects of TBC on 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in human dopaminergic neuroblastoma SH-SY5Y cells. TBC at concentrations from 0.1–10 μM had no toxic effect on HAPI cells and SH-SY5Y cells, and it inhibited LPS (100 ng/ml)-induced increases of superoxide, intracellular ROS, gp91 Phox, iNOS and a decrease of HO-1 in HAPI cells. Under coculture condition, TBC significantly reduced LPS-activated microglia-induced dopaminergic SH-SY5Y cells death. Moreover, TBC (0.1–10 μM) inhibited 6-OHDA-induced increases of intracellular ROS, iNOS, nNOS, and a decrease of mitochondria membrane potential, and cell death in SH-SY5Y cells. However, the neurotoxic effects of TBC (100 μM) on SH-SY5Y cells were also observed including the decrease in mitochondria membrane potential and the increase in COX-2 expression and cell death. TBC-induced SH-SY5Y cell death was attenuated by pretreatment with NS-398, a selective COX-2 inhibitor. In conclusion, this study suggests that TBC might possess protective effects on inflammation- and oxidative stress-related neurodegenerative disorders. However, the high concentration of TBC might be toxic, at least in part, for increasing COX-2 expression.

In vivo administration of D609 leads to protection of subsequently isolated gerbil brain mitochondria subjected to in vitro oxidative stress induced by amyloid beta-peptide and other oxidative stressors: Relevance to Alzheimer’s disease and other oxidative stress-related neurodegenerative disorders

Tricyclodecan-9-yl-xanthogenate (D609) has in vivo and in vitro antioxidant properties. D609 mimics glutathione (GSH) and has a free thiol group, which upon oxidation forms a disulfide. The resulting dixanthate is a substrate for glutathione reductase, regenerating D609. Recent studies have also shown that D609 protects brain in vivo and neuronal cultures in vitro against the potential Alzheimer’s disease (AD) causative factor, Aβ(1–42)-induced oxidative stress and cytotoxicity. Mitochondria are important organelles with both pro- and antiapoptotic factor proteins. The present study was undertaken to test the hypothesis that intraperitoneal injection of D609 would provide neuroprotection against free radical-induced, mitochondria-mediated apoptosis in vitro. Brain mitochondria were isolated from gerbils 1 h post injection intraperitoneally (ip) with D609 and subsequently treated in vitro with the oxidants Fe 2+/H 2O 2 (hydroxyl free radicals), 2,2-azobis-(2-amidinopropane) dihydrochloride (AAPH, alkoxyl and peroxyl free radicals), and AD-relevant amyloid β-peptide 1–42 [Aβ(1–42)]. Brain mitochondria isolated from the gerbils previously injected ip with D609 and subjected to these oxidative stress inducers, in vitro, showed significant reduction in levels of protein carbonyls, protein-bound hydroxynonenal [a lipid peroxidation product], 3-nitrotyrosine, and cytochrome c release compared to oxidant-treated brain mitochondria isolated from saline-injected gerbils. D609 treatment significantly maintains the GSH/GSSG ratio in oxidant-treated mitochondria. Increased activity of glutathione S-transferase, glutathione peroxidase, and glutathione reductase in brain isolated from D609-injected gerbils is consistent with the notion that D609 acts like GSH. These antiapoptotic findings are discussed with reference to the potential use of this brain-accessible glutathione mimetic in the treatment of oxidative stress-related neurodegenerative disorders, including AD.

In vivo protection of synaptosomes by ferulic acid ethyl ester (FAEE) from oxidative stress mediated by 2,2-azobis(2-amidino-propane)dihydrochloride (AAPH) or Fe 2+/H 2O 2: Insight into mechanisms of neuroprotection and relevance to oxidative stress-related neurodegenerative disorders

Ferulic acid ethyl ester (FAEE) is an ester derivative of ferulic acid, the latter known for its anti-inflammatory and antioxidant properties. Previous studies from our laboratory have shown that ferulic acid protects synaptosomal membrane system and neuronal cell culture systems against hydroxyl and peroxyl radical oxidation. FAEE is lipophilic and is able to penetrate lipid bilayer. Previous studies reported that FAEE reduces Alzheimer's amyloid β peptide Aβ(1–42)-induced oxidative stress and cytotoxicity in neuronal cell culture by direct radical scavenging and by inducing certain antioxidant proteins. In the present study we tested the hypothesis that FAEE would provide neuroprotection against free radical oxidative stress in vivo. Synaptosomes were isolated from the gerbils that were previously injected intraperitoneally (i.p.) with FAEE or DMSO and were treated with oxidants, Fe 2+/H 2O 2 or 2,2-azobis(2-amidino-propane)dihydrochloride (AAPH). Synaptosomes isolated from the gerbil previously injected i.p. with FAEE and treated with Fe 2+/H 2O 2 and AAPH showed significant reduction in reactive oxygen species (ROS), levels of protein carbonyl, protein bound 4-hydroxynonenal (HNE, a lipid peroxidation product), and 3-nitrotyrosine (3-NT, another marker of protein oxidation formed by reaction of tyrosine residues with peroxynitrite) compared to Fe 2+/H 2O 2 or AAPH induced oxidative stress in synapotosomes isolated from the brain of gerbils that were previously injected with DMSO. The synaptosomes isolated from gerbil pre-injected with FAEE and subsequently treated with AAPH or Fe 2+/H 2O 2 showed induction of heme oxygenase (HO-1) and heat shock protein 70 (HSP-70) but reduced inducible nitric oxide synthase (iNOS) levels. These results are discussed with reference to potential use of this lipophilic antioxidant phenolic compound in the treatment of oxidative stress-related neurodegenerative disorders.

Total antioxidant capacity is impaired in different structures from aged rat brain

Our data support a disproportion between free radicals levels and scavenging systems activity in different cerebral regions of the aging rat. We investigated the total reactive antioxidant potential and reactivity levels, which represent the total antioxidant capacity, in different cerebral regions of the aging rat (cortex, striatum, hippocampus and the cerebellum). In addition, we have determined several oxidative stress parameters, specifically the free radicals levels, the macromolecules damage (lipid peroxidation and carbonyl content), as well as the antioxidant enzymes activities in different cerebral areas from young (2 months-old), mature adult (6 months-old) and old (24 months-old) male Wistar rats. Free radicals levels, determined by 2′,7′-dichlorofluorescein diacetate probe, were higher in striatum, cerebellum and hippocampus from aged rats. There was an age-related increase in lipoperoxidation in hippocampus and cerebral cortex. In the cerebellum, a high activity of superoxide dismutase and a decrease of catalase activity were observed. The striatum exhibited a significant catalase activity decrease; and glutathione peroxidase activity was diminished in the hippocampus of mature and aged rats. There was a marked decrease of total antioxidant capacity in hippocampus in both reactivity and potential levels, whereas striatum and cerebral cortex displayed a reduction on reactivity assay. We suggest that age-related variations of total antioxidant defenses in brain may predispose structures to oxidative stress-related neurodegenerative disorders.

Redox proteomics identification of oxidatively modified proteins in Alzheimer's disease brain and in vivo and in vitro models of AD centered around Aβ(1–42)☆

Alzheimer's disease is a progressive neurodegenerative disease associated with loss of memory and cognition. One hallmark of AD is the accumulation of amyloid beta-peptide (Abeta), which invokes a cascade of oxidative damage to neurons that can eventually result in neuronal death. Several markers of oxidative stress have been identified in AD brain, thus providing greater understanding into potential mechanisms involved in the disease pathogenesis and progression. In the present article, we review the application of redox proteomics to the identification of oxidized proteins in AD brain and also our recent findings on amyloid beta-peptide (Abeta)-associated in vivo and in vitro models of AD. Our redox proteomics approach has made possible the identification of specifically oxidized proteins in Alzheimer's disease (AD) brain, providing for the first time evidence on how oxidative stress plays a crucial role in AD-related neurodegeneration. The information obtained has great potential to aid in determining the molecular pathogenesis in and detecting disease markers of AD, as well as identifying potential targets for drug therapy in AD. Application of redox proteomics to study cellular events, especially related to disease dysfunction, may provide an efficient tool to understand the main mechanisms involved in the pathogenesis and progression of oxidative stress-related neurodegenerative disorders.

In vivo protection of synaptosomes from oxidative stress mediated by Fe 2+/H 2O 2 or 2,2-azobis-(2-amidinopropane) dihydrochloride by the glutathione mimetic tricyclodecan-9-yl-xanthogenate

D609 (tricyclodecan-9-yl-xanthogenate) is a phosphatidylcholine-specific phospholipase C inhibitor that also has been reported to protect rodents against oxidative damage caused by lethal doses of ionizing radiation. We previously showed that D609 mimics glutathione. D609 has a free thiol group, which upon oxidation forms a disulfide. The resulting dixanthate is a substrate for glutathione reductase, regenerating D609. Recent studies from our laboratory have also shown that D609 reduces the Alzheimer amyloid β-peptide (1-42)-induced oxidative stress and cytotoxicity in neuronal cell culture. The present study was undertaken to test the hypothesis that D609 would provide neuroprotection against free radical oxidative stress in vivo. Synaptosomes isolated from gerbils, previously injected intraperitoneally (ip) with D609, were treated with the oxidants Fe 2+/H 2O 2 or 2,2-azobis-(2-amidinopropane) dihydrochloride (AAPH), which produce free radicals. Synaptosomes isolated from the gerbils ip injected with D609 and treated with Fe 2+/H 2O 2 or AAPH showed significant reduction in reactive oxygen species, levels of protein carbonyl, protein-bound hydroxynonenal (a lipid peroxidation product), and 3-nitrotyrosine (another marker of protein oxidation formed by reaction of tyrosine residues with peroxynitrite) compared to oxidative stress in synaptosomes isolated from gerbils that were injected with saline, but treated with Fe 2+/H 2O 2 or AAPH. These results are discussed with reference to the potential use of this brain-accessible glutathione mimetic in the treatment of oxidative stress-related neurodegenerative disorders.

Localization of α-tocopherol transfer protein in the brains of patients with ataxia with vitamin E deficiency and other oxidative stress related neurodegenerative disorders

Vitamin E (α-tocopherol) is an essential nutrient and an important antioxidant. Its plasma levels are dependent upon oral intake, absorption and transfer of the vitamin to a circulating lipoprotein. The latter step is controlled by α-tocopherol transfer protein (α-TTP), which is a 278 amino acid protein encoded on chromosome 8, known to be synthesized in the liver. Mutations in α-TTP are associated with a neurological syndrome of spinocerebellar ataxia, called ataxia with vitamin E deficiency (AVED). Earlier studies suggested that α-TTP is found only in the liver. In order to establish whether α-TTP is expressed in the human brain, and what relationship this has to AVED, we studied immunohistochemically the presence of α-TTP in the brains of a patient with AVED, normal subjects, and patients with Alzheimer's disease (AD), Down's syndrome (DS), cholestatic liver disease (CLD) and abetalipoproteinemia (ABL). The neuropathology of both AD and DS is thought to be related in part to oxidative stress. The diseases of AVED, of cholestatic liver disease, and of abetalipoproteinemia are thought to be due to lack of circulating tocopherol, leading to inadequate protection against oxidative damage. We demonstrate the presence of α-TTP in cerebellar Purkinje cells in patients having vitamin E deficiency states or diseases associated with oxidative stress.

Oxidant stress and the vascular endothelium: Mechanisms and therapeutic implications

Tricyclodecan-9-yl-xanthogenate (D609) has in vivo and in vitro antioxidant properties. D609 mimics glutathione (GSH) and has a free thiol group, which upon oxidation forms a disulfide. The resulting dixanthate is a substrate for glutathione reductase, regenerating D609. Recent studies have also shown that D609 protects brain in vivo and neuronal cultures in vitro against the potential Alzheimer’s disease (AD) causative factor, Aβ(1–42)-induced oxidative stress and cytotoxicity. Mitochondria are important organelles with both pro- and antiapoptotic factor proteins. The present study was undertaken to test the hypothesis that intraperitoneal injection of D609 would provide neuroprotection against free radical-induced, mitochondria-mediated apoptosis in vitro. Brain mitochondria were isolated from gerbils 1 h post injection intraperitoneally (ip) with D609 and subsequently treated in vitro with the oxidants Fe2+/H2O2 (hydroxyl free radicals), 2,2-azobis-(2-amidinopropane) dihydrochloride (AAPH, alkoxyl and peroxyl free radicals), and AD-relevant amyloid β-peptide 1–42 [Aβ(1–42)]. Brain mitochondria isolated from the gerbils previously injected ip with D609 and subjected to these oxidative stress inducers, in vitro, showed significant reduction in levels of protein carbonyls, protein-bound hydroxynonenal [a lipid peroxidation product], 3-nitrotyrosine, and cytochrome c release compared to oxidant-treated brain mitochondria isolated from saline-injected gerbils. D609 treatment significantly maintains the GSH/GSSG ratio in oxidant-treated mitochondria. Increased activity of glutathione S-transferase, glutathione peroxidase, and glutathione reductase in brain isolated from D609-injected gerbils is consistent with the notion that D609 acts like GSH. These antiapoptotic findings are discussed with reference to the potential use of this brain-accessible glutathione mimetic in the treatment of oxidative stress-related neurodegenerative disorders, including AD.