A novel thiol antioxidant that crosses the blood brain barrier protects dopaminergic neurons in experimental models of Parkinson's disease

Multifunctional redox modulator prevents blast-induced loss of cochlear and vestibular hair cells and auditory spiral ganglion neurons

Blast wave exposure, a leading cause of hearing loss and balance dysfunction among military personnel, arises primarily from direct mechanical damage to the mechanosensory hair cells and supporting structures or indirectly through excessive oxidative stress. We previously reported that HK-2, an orally active, multifunctional redox modulator (MFRM), was highly effective in reducing both hearing loss and hair cells loss in rats exposed to a moderate intensity workday noise that likely damages the cochlea primarily from oxidative stress versus direct mechanical trauma. To determine if HK-2 could also protect cochlear and vestibular cells from damage caused primarily from direct blast-induced mechanical trauma versus oxidative stress, we exposed rats to six blasts of 186 dB peak SPL. The rats were divided into four groups: (B) blast alone, (BEP) blast plus earplugs, (BHK-2) blast plus HK-2 and (BEPHK-2) blast plus earplugs plus HK-2. HK-2 was orally administered at 50 mg/kg/d from 7-days before to 30-day after the blast exposure. Cochlear and vestibular tissues were harvested 60-d post-exposure and evaluated for loss of outer hair cells (OHC), inner hair cells (IHC), auditory nerve fibers (ANF), spiral ganglion neurons (SGN) and vestibular hair cells in the saccule, utricle and semicircular canals. In the untreated blast-exposed group (B), massive losses occurred to OHC, IHC, ANF, SGN and only the vestibular hair cells in the striola region of the saccule. In contrast, rats treated with HK-2 (BHK-2) sustained significantly less OHC (67%) and IHC (57%) loss compared to the B group. OHC and IHC losses were smallest in the BEPHK-2 group, but not significantly different from the BEP group indicating lack of protective synergy between EP and HK-2. There was no loss of ANF, SGN or saccular hair cells in the BHK-2, BEP and BEPHK-2 groups. Thus, HK-2 not only significantly reduced OHC and IHC damage, but completely prevented loss of ANF, SGN and saccule hair cells. The powerful protective effects of this oral MFRM make HK-2 an extremely promising candidate for human clinical trials.

Lipophilic analogues of D-cysteine prevent and reverse physical dependence to fentanyl in male rats

We examined whether co-injections of the cell-permeant D-cysteine analogues, D-cysteine ethyl ester (D-CYSee) and D-cysteine ethyl amide (D-CYSea), prevent acquisition of physical dependence induced by twice-daily injections of fentanyl, and reverse acquired dependence to these injections in freely-moving male Sprague Dawley rats. Injection of the opioid receptor antagonist, naloxone HCl (NLX, 1.5 mg/kg, IV), elicited a series of withdrawal phenomena that included cardiorespiratory and behavioral responses, and falls in body weight and body temperature, in rats that received 5 or 10 injections of fentanyl (125 μg/kg, IV), and the same number of vehicle co-injections. Regarding the development of physical dependence, the NLX-precipitated withdrawal phenomena were markedly reduced in fentanyl-injected rats that had received co-injections of D-CYSee (250 μmol/kg, IV) or D-CYSea (100 μmol/kg, IV), but not D-cysteine (250 μmol/kg, IV). Regarding reversal of established dependence to fentanyl, the NLX-precipitated withdrawal phenomena in rats that had received 10 injections of fentanyl (125 μg/kg, IV) was markedly reduced in rats that received co-injections of D-CYSee (250 μmol/kg, IV) or D-CYSea (100 μmol/kg, IV), but not D-cysteine (250 μmol/kg, IV), starting with injection 6 of fentanyl. This study provides evidence that co-injections of D-CYSee and D-CYSea prevent the acquisition of physical dependence, and reverse acquired dependence to fentanyl in male rats. The lack of effect of D-cysteine suggests that the enhanced cell-penetrability of D-CYSee and D-CYSea into cells, particularly within the brain, is key to their ability to interact with intracellular signaling events involved in acquisition to physical dependence to fentanyl.

N-Acetylcysteine amide (NACA) and diNACA inhibit H2O2-induced cataract formation ex vivo in pig and rat lenses

Oxidative stress plays a central role in cataract formation suggesting that antioxidants might slow cataract progression. The anticataract activity of N-acetylcysteine amide (NACA) and (2 R, 2 R')-3,3'-disulfanediyl bis(2-acetamidopropanamide) (diNACA) and/or N-acetylcysteine (NAC), were evaluated in porcine and rat lens models. Cataractogenesis via oxidation was induced with H2O2 and/or glucose oxidase (GO). Porcine lenses were incubated in 0.1 mM, 1 mM, or 10 mM NAC, NACA or diNACA for 24 h. Lenses were then transferred to media containing 0.75 mM H2O2 and 4.63U of GO in order to maintain a constant H2O2 level for an additional 8 h. At the end of incubation, lenses were imaged under darkfield microscopy. Separately, rat lenses were extracted from 3-week-old Wistar rats and incubated with either 10 mM NACA or 10 mM diNACA for 24 h prior to treatment with 0.2U GO to generate a steady source of ∼0.6 mM H2O2. Rat lenses were analyzed by LC-MS/MS to quantify changes in cysteine, cystine, glutathione (GSH) or oxidised glutathione (GSSG) levels in the lens epithelium, cortex or core. Pre-treatment with NACA or diNACA followed by oxidation with H2O2 and/or GO to stimulate cataract formation afforded rapid assessment in ex vivo porcine (32 h) and rat (48 h) lens models. Pre-treatment of isolated porcine lenses with 0.1 mM, 1 mM or 10 mM of either NAC, NACA or diNACA followed by H2O2/GO treatment resulted in reduced lens opacity relative to the lenses exposed to H2O2/GO, with NACA and diNACA reducing opacities to a greater extent than NAC. Rat lenses incubated with 10 mM NACA or 10 mM diNACA without exposure to H2O2 showed no signs of opacities. Pre-treatment of rat lenses with 10 mM NACA or 10 mM diNACA, followed by GO cataract induction resulted in reduced opacities compared to control (GO alone). LC-MS/MS analyses revealed that NACA, but not diNACA, increased cysteine, cystine and GSH levels in rat lens epithelium and cortex regions. Taken together, both NACA and diNACA inhibited cataract formation to a greater extent than NAC (all at 1-10 mM) in an ex vivo porcine lens model. Both NACA and diNACA (both at 10 mM) reduced cataract formation in rat lenses. Based on LC-MS/MS analyses, NACA-induced reduction in opacity observed in rat lenses was attributed to enhanced cysteine and GSH levels while the diNACA-induced reduction in opacity induced did not consistently increase cysteine, cystine and GSH levels and, therefore, appears to involve a different antioxidant mechanism. These screening studies warrant further testing of NACA and diNACA as anticataract agents.

Secondary Mitochondrial Dysfunction as a Cause of Neurodegenerative Dysfunction in Lysosomal Storage Diseases and an Overview of Potential Therapies

Mitochondrial dysfunction has been recognised a major contributory factor to the pathophysiology of a number of lysosomal storage disorders (LSDs). The cause of mitochondrial dysfunction in LSDs is as yet uncertain, but appears to be triggered by a number of different factors, although oxidative stress and impaired mitophagy appear to be common inhibitory mechanisms shared amongst this group of disorders, including Gaucher’s disease, Niemann–Pick disease, type C, and mucopolysaccharidosis. Many LSDs resulting from defects in lysosomal hydrolase activity show neurodegeneration, which remains challenging to treat. Currently available curative therapies are not sufficient to meet patients’ needs. In view of the documented evidence of mitochondrial dysfunction in the neurodegeneration of LSDs, along with the reciprocal interaction between the mitochondrion and the lysosome, novel therapeutic strategies that target the impairment in both of these organelles could be considered in the clinical management of the long-term neurodegenerative complications of these diseases. The purpose of this review is to outline the putative mechanisms that may be responsible for the reported mitochondrial dysfunction in LSDs and to discuss the new potential therapeutic developments.

Novel anti-apoptotic L-DOPA precursors SuperDopa and SuperDopamide as potential neuroprotective agents for halting/delaying progression of Parkinson’s disease

Parkinson’s disease (PD) is characterized by a gradual degeneration of the dopaminergic neurons in the substantia nigra pars compacta (SNpC). Levodopa, the standard PD treatment, provides the missing dopamine in SNpC, but ultimately after a honeymoon with levodopa treatment the neurodegenerative process and the progression of the disease continue. Aimed at prolonging the life of dopaminergic cells, we prepared the levodopa precursors SuperDopa (SD) and SueprDopamide (SDA), in which levodopa is merged with the antioxidant N-acetylcysteine (NAC) into a single molecule. Rotenone is a mitochondrial complex inhibitor often used as experimental model of PD. In vivo, SD and SDA treatment show a significant relief of motor disabilities in rotenone-injected rats. SD and SDA also lower rotenone-induced-α-synuclein (α-syn) expression in human SH-SY5Y cells, and α-syn oligomerization in α-syn-overexpressing-HEK293 cells. In the neuronal SH-SY5Y cells, SD and SDA reverse oxidative stress-induced phosphorylation of cJun-N-terminal kinase (JNK) and p38-mitogen-activated kinase (p38^MAPK). Attenuation of the MAPK-inflammatory/apoptotic pathway in SH-SY5Y cells concurrent with protection of rotenone-triggered motor impairment in rats, is a manifestation of the combined antioxidant/anti-inflammatory activity of SD and SDA together with levodopa release. The concept of joined therapies into a single molecule, where levodopa precursors confer antioxidant activity by enabling NAC delivery across the BBB, provides a potential disease-modifying treatment for slowing PD progression.

Variable fluid flow regimes alter human brain microvascular endothelial cell-cell junctions and cytoskeletal structure

The human brain microvasculature is constantly exposed to variable fluid flow regimes and their influence on the endothelium depends in part on the synchronous cooperative behavior between cell-cell junctions and the cytoskeleton. In this study, we exposed human cerebral microvascular endothelial cells to a low laminar flow (1 dyne⋅cm^-2 ), high laminar flow (10 dyne⋅cm^-2 ), low oscillatory flow (±1 dyne⋅cm^-2 ), or high oscillatory flow (±10 dyne⋅cm^-2 ) for 24 hr. After this time, endothelial cell-cell junction and cytoskeletal structural response was characterized through observation of zonula occludens-1 (ZO-1), claudin-5, junctional adhesion molecule-A (JAM-A), vascular endothelial cadherin (VE-Cad), and F-actin. In addition, we also characterized cell morphology through measurement of cell area and cell eccentricity. Our results revealed the greatest change in junctional structure reorganization for ZO-1 and JAM-A to be observed under low laminar flow conditions while claudin-5 exhibited the greatest change in structural reorganization under both low and high laminar flow conditions. However, VE-Cad displayed the greatest structural response under a high laminar flow, reflecting the unique responses each cell-cell junction protein had to each fluid flow regime. In addition, cell area and cell eccentricity displayed most significant changes under the high laminar flow and low oscillatory flow, respectively. We believe this study will be useful to the field of cell mechanics and mechanobiology.

Continuous Monitoring Reveals Protective Effects of N-Acetylcysteine Amide on an Isogenic Microphysiological Model of the Neurovascular Unit

Microphysiological systems mimic the in vivo cellular ensemble and microenvironment with the goal of providing more human-like models for biopharmaceutical research. In this study, the first such model of the blood-brain barrier (BBB-on-chip) featuring both isogenic human induced pluripotent stem cell (hiPSC)-derived cells and continuous barrier integrity monitoring with <2 min temporal resolution is reported. Its capabilities are showcased in the first microphysiological study of nitrosative stress and antioxidant prophylaxis. Relying on off-stoichiometry thiol-ene-epoxy (OSTE+) for fabrication greatly facilitates assembly and sensor integration compared to the prevalent polydimethylsiloxane devices. The integrated cell-substrate endothelial resistance monitoring allows for capturing the formation and breakdown of the BBB model, which consists of cocultured hiPSC-derived endothelial-like and astrocyte-like cells. Clear cellular disruption is observed when exposing the BBB-on-chip to the nitrosative stressor linsidomine, and the barrier permeability and barrier-protective effects of the antioxidant N-acetylcysteine amide are reported. Using metabolomic network analysis reveals further drug-induced changes consistent with prior literature regarding, e.g., cysteine and glutathione involvement. A model like this opens new possibilities for drug screening studies and personalized medicine, relying solely on isogenic human-derived cells and providing high-resolution temporal readouts that can help in pharmacodynamic studies.

Diet with Low Molecular Weight Chitosan exerts neuromodulation in Rotenone induced Drosophila model of Parkinson's disease

Rotenone (ROT) is well known pesticide been used in agriculture due to its low cost and rapid action. This has also been widely used to establish Parkinson's disease (PD) models in rodents. Here we have evaluated the role of well established potent molecule 'Low Molecular Weight Chitosan (LMWC)' against ROT induced neurotoxicity in Drosophila melanogaster. Male adult flies (8-10 days) were induced for neurotoxicity using ROT (500 μM) and treated with LMWC (5 & 10 mg/mL basal media) during 7 days experiment. Subsequently, neurodegenerative and behavioural parameters were assessed. As a result, flies exposed to ROT alone showed decreased locomotor behaviour in negative geotaxis and open-field studies and had a higher incidence of mortality compared to control group. These effects were accompanied by decrease in dopamine level, ETC complexes and increase in reactive oxygen species (ROS) production and cholinergic activities in head and body of the flies, suggesting ROT was able to induce oxidative stress. Co-exposure of LMWC reversed the ROT induced locomotor impairment, exploratory deficits and changes the biochemical parameters to normal level and increased the survival rate to 16 days. Thus, we suggested LMWC may be considered as better supplement in the prevention and management of Parkinson's disease.

Spotlight on Ferroptosis: Iron-Dependent Cell Death in Alzheimer's Disease

Alzheimer's disease is an emerging global epidemic that is becoming increasingly unsustainable. Most of the clinical trials have been centered around targeting β-amyloid and have met with limited success. There is a great impetus to identify alternative drug targets. Iron appears to be the common theme prevalent across neurodegenerative diseases. Iron has been shown to promote aggregation and pathogenicity of the characteristic aberrant proteins, β-amyloid, tau, α-synuclein, and TDP43, in these diseases. Further support for the involvement of iron in pathogenesis is provided by the recent discovery of a new form of cell death, ferroptosis. Arising from iron-dependent lipid peroxidation, ferroptosis is augmented in conditions of cysteine deficiency and glutathione peroxidase-4 inactivation. Here, we review clinical trials that provide the rationale for targeting ferroptosis to delay the pathogenesis of Alzheimer's disease (AD), potentially of relevance to other neurodegenerative diseases.

Effects of N-acetylcysteine amide on anxiety and stress behavior in zebrafish

Anxiety disorders are highly prevalent and a leading cause of disability worldwide. Their etiology is related to stress, an adaptive response of the organism to restore homeostasis, in which oxidative stress and glutamatergic hyperactivity are involved. N-Acetylcysteine (NAC) is a multitarget approved drug proved to be beneficial in the treatment of various mental disorders. Nevertheless, NAC has low membrane permeability and poor bioavailability and its limited delivery to the brain may explain inconsistencies in the literature. N-Acetylcysteine amide (AD4) is a synthetic derivative of NAC in which the carboxyl group was modified to an amide. The amidation of AD4 improved lipophilicity and blood-brain barrier permeability and enhanced its antioxidant properties. The purpose of this study was to investigate the effects of AD4 on behavioral and biochemical parameters in zebrafish anxiety models. Neither AD4 nor NAC induced effects on locomotion and anxiety-related parameters in the novel tank test. However, in the light/dark test, AD4 (0.001 mg/L) increased the time spent in the lit side in a concentration 100 times lower than NAC (0.1 mg/L). In the acute restraint stress protocol, NAC and AD4 (0.001 mg/L) showed anxiolytic properties without meaningful effects on oxidative status. The study suggests that AD4 has anxiolytic effects in zebrafish with higher potency than the parent compound. Additional studies are warranted to characterize the anxiolytic profile of AD4 and its potential in the management of anxiety disorders.

Neurotheranostics as personalized medicines

The discipline of neurotheranostics was forged to improve diagnostic and therapeutic clinical outcomes for neurological disorders. Research was facilitated, in largest measure, by the creation of pharmacologically effective multimodal pharmaceutical formulations. Deployment of neurotheranostic agents could revolutionize staging and improve nervous system disease therapeutic outcomes. However, obstacles in formulation design, drug loading and payload delivery still remain. These will certainly be aided by multidisciplinary basic research and clinical teams with pharmacology, nanotechnology, neuroscience and pharmaceutic expertise. When successful the end results will provide "optimal" therapeutic delivery platforms. The current report reviews an extensive body of knowledge of the natural history, epidemiology, pathogenesis and therapeutics of neurologic disease with an eye on how, when and under what circumstances neurotheranostics will soon be used as personalized medicines for a broad range of neurodegenerative, neuroinflammatory and neuroinfectious diseases.

7-chloro-4-(phenylselanyl) quinoline prevents dopamine depletion in a Drosophila melanogaster model of Parkinson's-like disease

Neurodegeneration in Parkinson's disease appears to be caused by multiple factors, including oxidative damage and an increase in acetylcholinesterase expression that can culminate in loss of dopaminergic neurons. A selenium-containing quinoline derivative, 7-chloro-4-(phenylselanyl) quinoline (4-PSQ), shows important pharmacological actions mainly attributed to its antioxidant and anticholinesterase properties. Thus, this study investigated the neuroprotective effect of 4-PSQ in a model of Parkinson's-like disease induced by rotenone (ROT) in Drosophila melanogaster and verified whether these effects are related to selenium levels. Adult flies were divided into: [1] control, [2] 4-PSQ (25 μM), [3] ROT (500 μM), and [4] 4-PSQ (25 μM) + ROT (500 μM) groups and exposed to a diet containing ROT and/or 4-PSQ for 7 days, according to their respective groups. Survival, behavioral, and ex vivo analyses were performed. Dopamine levels, reactive species levels (RS), lipid peroxidation (LPO), superoxide dismutase (SOD) and catalase (CAT) activity, and proteic thiol (PSH) and non-proteic thiol (NPSH) content in the head region were analyzed, while acetylcholinesterase (AChE) activity and selenium levels in the head and body regions were analyzed. 4-PSQ was able to reverse the ROT-induced deficits in flies, reestablish dopamine and selenium levels, reverse cholinergic deficits, improve motor function, and ameliorate mortality. Furthermore, 4-PSQ also reduced RS levels and LPO, and restored the activities of the antioxidant enzymes, SOD and CAT. Interestingly, a positive relationship between dopamine and selenium levels could be seen. Our results demonstrate the neuroprotective effect of 4-PSQ, and we suggest that the compound may act via different mechanisms, such as improving antioxidant defenses and consequently reducing oxidative damages, as well as having an anticholinesterase action, which together can prevent dopamine depletion, as these actions were correlated with the presence of selenium in the 4-PSQ molecule.

Boosting GSH Using the Co-Drug Approach: I-152, a Conjugate of N-acetyl-cysteine and β-mercaptoethylamine

Glutathione (GSH) has poor pharmacokinetic properties; thus, several derivatives and biosynthetic precursors have been proposed as GSH-boosting drugs. I-152 is a conjugate of N-acetyl-cysteine (NAC) and S-acetyl-β-mercaptoethylamine (SMEA) designed to release the parent drugs (i.e., NAC and β-mercaptoethylamine or cysteamine, MEA). NAC is a precursor of L-cysteine, while MEA is an aminothiol able to increase GSH content; thus, I-152 represents the very first attempt to combine two pro-GSH molecules. In this review, the in-vitro and in-vivo metabolism, pro-GSH activity and antiviral and immunomodulatory properties of I-152 are discussed. Under physiological GSH conditions, low I-152 doses increase cellular GSH content; by contrast, high doses cause GSH depletion but yield a high content of NAC, MEA and I-152, which can be used to resynthesize GSH. Preliminary in-vivo studies suggest that the molecule reaches mouse organs, including the brain, where its metabolites, NAC and MEA, are detected. In cell cultures, I-152 replenishes experimentally depleted GSH levels. Moreover, administration of I-152 to C57BL/6 mice infected with the retroviral complex LP-BM5 is effective in contrasting virus-induced GSH depletion, exerting at the same time antiviral and immunomodulatory functions. I-152 acts as a pro-GSH agent; however, GSH derivatives and NAC cannot completely replicate its effects. The co-delivery of different thiol species may lead to unpredictable outcomes, which warrant further investigation.

(E)-2-methoxy-4-(3-(4-methoxyphenyl) prop-1-en-1-yl) Phenol Ameliorates MPTP-Induced Dopaminergic Neurodegeneration by Inhibiting the STAT3 Pathway

Neuroinflammation is implicated in dopaminergic neurodegeneration. We have previously demonstrated that (E)-2-methoxy-4-(3-(4-methoxyphenyl) prop-1-en-1-yl) phenol (MMPP), a selective signal transducer and activator of transcription 3 (STAT3) inhibitor, has anti-inflammatory properties in several inflammatory disease models. We investigated whether MMPP could protect against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopaminergic cell loss and behavioral impairment. Imprinting control region (ICR) mice (8 weeks old, n = 10 per group) were administered MMPP (5 mg/kg) in drinking water for 1 month, and injected with MPTP (15 mg/kg, four times with 2 h intervals) during the last 7 days of treatment. MMPP decreased MPTP-induced behavioral impairments in rotarod, pole, and gait tests. We also showed that MMPP ameliorated dopamine depletion in the striatum and inflammatory marker elevation in primary cultured neurons by high-performance liquid chromatography and immunohistochemical analysis. Increased activation of STAT3, p38, and monoamine oxidase B (MAO-B) were observed in the substantia nigra and striatum after MPTP injection, effects that were attenuated by MMPP treatment. Furthermore, MMPP inhibited STAT3 activity and expression of neuroinflammatory proteins, including ionized calcium binding adaptor molecule 1 (Iba1), inducible nitric oxide synthase (iNOS), and glial fibrillary acidic protein (GFAP) in 1-methyl-4-phenylpyridinium (MPP⁺; 0.5 mM)-treated primary cultured cells. However, mitogen-activated protein kinase (MAPK) inhibitors augmented the activity of MMPP. Collectively, our results suggest that MMPP may be an anti-inflammatory agent that attenuates dopaminergic neurodegeneration and neuroinflammation through MAO-B and MAPK pathway-dependent inhibition of STAT3 activation.

Linking mitochondrial dysfunction to neurodegeneration in lysosomal storage diseases

Lysosomal storage diseases (LSD) are inborn errors of metabolism resulting in multisystem disease. Central nervous system involvement, often with progressive neurodegeneration, accounts for a large portion of the morbidity and mortality seen in many LSD. Available treatments fail to prevent or correct neurologic symptoms and decline. Emerging evidence points to an important role for mitochondrial dysfunction in the pathogenesis and progression of LSD-associated neurodegeneration. Mitochondrial dysfunction in LSD is characterized by alterations in mitochondrial mass, morphology and function. Disturbed mitochondrial metabolism in the CNS may lead to excessive production of mitochondrial reactive oxygen species and dysregulated calcium homeostasis. These metabolic disturbances ultimately result in mitochondria-induced apoptosis and neuronal degeneration. Here, we review the current evidence for mitochondrial dysfunction in neuronal models of seven LSD, including GM1-gangliosidosis, mucopolysaccharidosis IIIC, multiple sulfatase deficiency, Krabbe disease, Gaucher disease, Niemann Pick disease type C and the neural ceroid lipofuscinoses and outline current experimental therapies aimed at restoring mitochondrial function and neuroprotection in LSD.

N-acetylcysteine amide (AD4) reduces cocaine-induced reinstatement

RATIONALE

Chronic exposure to drugs of abuse changes glutamatergic transmission in human addicts and animal models. N-acetylcysteine (NAC) is a cysteine prodrug that indirectly activates cysteine-glutamate antiporters. In the extrasynaptic space, NAC restores basal glutamate levels during drug abstinence and normalizes increased glutamatergic tone in rats during reinstatement to drugs of abuse. In initial clinical trials, repeated NAC administration seems to be promising for reduced craving in cocaine addicts.

OBJECTIVE

In this study, NAC-amide, called AD4 or NACA, was examined in intravenous cocaine self-administration and extinction/reinstatement procedures in rats. We investigated the behavioral effects of AD4 in the olfactory bulbectomized (OBX) rats, considered an animal model of depression. Finally, we tested rats injected with AD4 or NAC during 10-daily extinction training sessions to examine subsequent cocaine seeking.

RESULTS

AD4 (25-75 mg kg(-1)) given acutely did not alter the rewarding effects of cocaine in OBX rats and sham-operated controls. However, at 6.25-50 mg kg(-1), AD4 decreased dose-dependently cocaine seeking and relapse triggered by cocaine priming or drug-associated conditioned cues in both phenotypes. Furthermore, repeated treatment with AD4 (25 mg kg(-1)) or NAC (100 mg kg(-1)) during daily extinction trials reduced reinstatement of drug-seeking behavior in sham-operated controls. In the OBX rats only, AD4 effectively blocked cocaine-seeking behavior.

CONCLUSIONS

Our results demonstrate that AD4 is effective at blocking cocaine-seeking behavior, highlighting its potential clinical use toward cocaine use disorder.

Thioredoxin-Mimetic-Peptides Protect Cognitive Function after Mild Traumatic Brain Injury (mTBI)

Mild traumatic brain injury (mTBI) is recognized as a common injury among children, sportsmen, and elderly population. mTBI lacks visible objective structural brain damage but patients frequently suffer from long-lasting cognitive, behavioral and emotional difficulties associated with biochemical and cellular changes. Currently there is no effective treatment for patients with mTBI. The thioredoxin reductase/thioredoxin pathway (TrxR/Trx1) has both anti-inflammatory and anti-oxidative properties. If the system is compromised, Trx1 remains oxidized and triggers cell death via an ASK1-Trx1 signal transduction mechanism. We previously showed tri and tetra peptides which were derived from the canonical -CxxC- motif of the Trx1-active site, called thioredoxin mimetic (TXM) peptides, reversed inflammatory and oxidative stress damage mimicking Trx1 activity. Here, TXM-peptides were examined for protecting cognitive function following weight drop closed-head injury in a mouse model of mTBI. TXM-CB3 (AcCys-Pro-CysNH₂), TXM-CB13 (DY-70; AcCys-Met-Lys-CysNH₂) or AD4 (ACysNH₂) were administered at 50 mg/kg, 60 min after injury and cognitive performance was monitored by the novel-object-recognition and Y-maze tests. Behavioral deficits subsequent to mTBI injury were reversed by a single dose of TXM-CB3, TXM-CB13 and, to a lesser extent, by AD4. TXM-CB13 similar to TXM-CB3 and AD4 reversed oxidative stress-induced phosphorylation of mitogen-activated kinases, p38^MAPK and c-Jun N-terminal kinase, (JNK) in human neuronal SH-SY5Y cells. We conclude that significantly improved cognitive behavior post mTBI by the TXM-peptides could result from anti-apoptotic, and/or anti-inflammatory activities. Future preclinical studies are required to establish the TXM-peptides as potential therapeutic drugs for brain injuries.

Neuroprotective effects of N-acetylcysteine amide on experimental focal penetrating brain injury in rats

We examined the effects of N-acetylcysteine amide (NACA) in the secondary inflammatory response following a novel method of focal penetrating traumatic brain injury (TBI) in rats. N-acetylcysteine (NAC) has limited but well-documented neuroprotective effects after experimental central nervous system ischemia and TBI, but its bioavailability is very low. We tested NACA, a modified form of NAC with higher membrane and blood-brain barrier permeability. Focal penetrating TBI was produced in male Sprague-Dawley rats randomly selected for NACA treatment (n=5) and no treatment (n=5). In addition, four animals were submitted to sham surgery. After 2 hours or 24 hours the brains were removed, fresh frozen, cut in 14 μm coronal sections and subjected to immunohistochemistry, immunofluorescence, Fluoro-Jade and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) analyses. All treated animals were given 300 mg/kg NACA intraperitoneally (IP) 2 minutes post trauma. The 24 hour survival group was given an additional bolus of 300 mg/kg IP after 4 hours. NACA treatment decreased neuronal degeneration by Fluoro-Jade at 24 hours with a mean change of 35.0% (p<0.05) and decreased TUNEL staining indicative of apoptosis at 2 hours with a mean change of 38.7% (p<0.05). Manganese superoxide dismutase (MnSOD) increased in the NACA treatment group at 24 hours with a mean change of 35.9% (p<0.05). Levels of migrating macrophages and activated microglia (Ox-42/CD11b), nitric oxide-producing inflammatory enzyme iNOS, peroxynitrite marker 3-nitrotyrosine, NFκB translocated to the nuclei, cytochrome C and Bcl-2 were not affected. NACA treatment decreased neuronal degeneration and apoptosis and increased levels of antioxidative enzyme MnSOD. The antiapoptotic effect was likely regulated by pathways other than cytochrome C. Therefore, NACA prevents brain tissue damage after focal penetrating TBI, warranting further studies towards a clinical application.

N-acetylcysteineamide protects against manganese-induced toxicity in SHSY5Y cell line

Manganese (Mn) is an essential trace element required for normal cellular functioning. However, overexposure of Mn can be neurotoxic resulting in the development of manganism, a syndrome that resembles Parkinson׳s disease. Although the pathogenetic basis of this disorder is unclear, several studies indicate that it is mainly associated with oxidative stress and mitochondrial energy failure. Therefore, this study is focused on (1) investigating the oxidative effects of Mn on neuroblastoma cells (SHSY5Y) and (2) elucidating whether a novel thiol antioxidant, N-acetylcysteineamide (NACA), provides any protection against Mn-induced neurotoxicity. Reactive oxygen species (ROS) were highly elevated after the exposure, indicating that mechanisms that induce oxidative stress were involved. Measures of oxidative stress parameters, such as glutathione (GSH), malondialdehyde (MDA), and activities of glutathione reductase (GR) and glutathione peroxidase (GPx) were altered in the Mn-treated groups. Loss of mitochondrial membrane potential, as assessed by flow cytometry and decreased levels of ATP, indicated that cytotoxicity was mediated through mitochondrial dysfunction. However, pretreatment with NACA protected against Mn-induced toxicity by inhibiting lipid peroxidation, scavenging ROS, and preserving intracellular GSH and mitochondrial membrane potential. NACA can potentially be developed into a promising therapeutic option for Mn-induced neurotoxicity. This article is part of a Special Issue entitled SI: Metals in neurodegeneration.

Repeated intratracheal instillation of PM10 induces lipid reshaping in lung parenchyma and in extra-pulmonary tissues

Adverse health effects of air pollution attributed mainly to airborne particulate matter have been well documented in the last couple of decades. Short term exposure, referring to a few hours exposure, to high ambient PM10 concentration is linked to increased hospitalization rates for cardiovascular events, typically 24 h after air pollution peaks. Particulate matter exposure is related to pulmonary and cardiovascular diseases, with increased oxidative stress and inflammatory status. Previously, we have demonstrated that repeated intratracheal instillation of PM10sum in BALB/c mice leads to respiratory tract inflammation, creating in lung a condition which could potentially evolve in a systemic toxic reaction. Additionally, plasma membrane and tissue lipids are easily affected by oxidative stress and directly correlated with inflammatory products. With this aim, in the present investigation using the same model, we analyzed the toxic potential of PM10sum exposure on lipid plasma membrane composition, lipid peroxidation and the mechanisms of cells protection in multiple organs such as lung, heart, liver and brain. Obtained results indicated that PM10 exposure led to lung lipid reshaping, in particular phospholipid and cholesterol content increases; concomitantly, the generation of oxidative stress caused lipid peroxidation. In liver we found significant changes in lipid content, mainly due to an increase of phosphatidylcholine, and in total fatty acid composition with a more pronounced level of docosahexaenoic acid; these changes were statistically correlated to lung molecular markers. Heart and brain were similarly affected; heart was significantly enriched in triglycerides in half of the PM10sum treated mice. These results demonstrated a direct involvement of PM10sum in affecting lipid metabolism and oxidative stress in peripheral tissues that might be related to the serious systemic air-pollution effects on human health.

N-acetylcysteine amide preserves mitochondrial bioenergetics and improves functional recovery following spinal trauma

Mitochondrial dysfunction is becoming a pivotal target for neuroprotective strategies following contusion spinal cord injury (SCI) and the pharmacological compounds that maintain mitochondrial function confer neuroprotection and improve long-term hindlimb function after injury. In the current study we evaluated the efficacy of cell-permeating thiol, N-acetylcysteine amide (NACA), a precursor of endogenous antioxidant glutathione (GSH), on mitochondrial function acutely, and long-term tissue sparing and hindlimb locomotor recovery following upper lumbar contusion SCI. Some designated injured adult female Sprague-Dawley rats (n=120) received either vehicle or NACA (75, 150, 300 or 600mg/kg) at 15min and 6h post-injury. After 24h the total, synaptic, and non-synaptic mitochondrial populations were isolated from a single 1.5cm spinal cord segment (centered at injury site) and assessed for mitochondrial bioenergetics. Results showed compromised total mitochondrial bioenergetics following acute SCI that was significantly improved with NACA treatment in a dose-dependent manner, with maximum effects at 300mg/kg (n=4/group). For synaptic and non-synaptic mitochondria, only 300mg/kg NACA dosage showed efficacy. Similar dosage (300mg/kg) also maintained mitochondrial GSH near normal levels. Other designated injured rats (n=21) received continuous NACA (150 or 300mg/kg/day) treatment starting at 15min post-injury for one week to assess long-term functional recovery over 6weeks post-injury. Locomotor testing and novel gait analyses showed significantly improved hindlimb function with NACA that were associated with increased tissue sparing at the injury site. Overall, NACA treatment significantly maintained acute mitochondrial bioenergetics and normalized GSH levels following SCI, and prolonged delivery resulted in significant tissue sparing and improved recovery of hindlimb function.

N-acetylcysteine amide preserves mitochondrial bioenergetics and improves functional recovery following spinal trauma

Mitochondrial dysfunction is becoming a pivotal target for neuroprotective strategies following contusion spinal cord injury (SCI) and the pharmacological compounds that maintain mitochondrial function confer neuroprotection and improve long-term hindlimb function after injury. In the current study we evaluated the efficacy of cell-permeating thiol, N-acetylcysteine amide (NACA), a precursor of endogenous antioxidant glutathione (GSH), on mitochondrial function acutely, and long-term tissue sparing and hindlimb locomotor recovery following upper lumbar contusion SCI. Some designated injured adult female Sprague-Dawley rats (n=120) received either vehicle or NACA (75, 150, 300 or 600mg/kg) at 15min and 6h post-injury. After 24h the total, synaptic, and non-synaptic mitochondrial populations were isolated from a single 1.5cm spinal cord segment (centered at injury site) and assessed for mitochondrial bioenergetics. Results showed compromised total mitochondrial bioenergetics following acute SCI that was significantly improved with NACA treatment in a dose-dependent manner, with maximum effects at 300mg/kg (n=4/group). For synaptic and non-synaptic mitochondria, only 300mg/kg NACA dosage showed efficacy. Similar dosage (300mg/kg) also maintained mitochondrial GSH near normal levels. Other designated injured rats (n=21) received continuous NACA (150 or 300mg/kg/day) treatment starting at 15min post-injury for one week to assess long-term functional recovery over 6weeks post-injury. Locomotor testing and novel gait analyses showed significantly improved hindlimb function with NACA that were associated with increased tissue sparing at the injury site. Overall, NACA treatment significantly maintained acute mitochondrial bioenergetics and normalized GSH levels following SCI, and prolonged delivery resulted in significant tissue sparing and improved recovery of hindlimb function.

Autophagy as an essential cellular antioxidant pathway in neurodegenerative disease

Oxidative stress including DNA damage, increased lipid and protein oxidation, are important features of aging and neurodegeneration suggesting that endogenous antioxidant protective pathways are inadequate or overwhelmed. Importantly, oxidative protein damage contributes to age-dependent accumulation of dysfunctional mitochondria or protein aggregates. In addition, environmental toxins such as rotenone and paraquat, which are risk factors for the pathogenesis of neurodegenerative diseases, also promote protein oxidation. The obvious approach of supplementing the primary antioxidant systems designed to suppress the initiation of oxidative stress has been tested in animal models and positive results were obtained. However, these findings have not been effectively translated to treating human patients, and clinical trials for antioxidant therapies using radical scavenging molecules such as α-tocopherol, ascorbate and coenzyme Q have met with limited success, highlighting several limitations to this approach. These could include: (1) radical scavenging antioxidants cannot reverse established damage to proteins and organelles; (2) radical scavenging antioxidants are oxidant specific, and can only be effective if the specific mechanism for neurodegeneration involves the reactive species to which they are targeted and (3) since reactive species play an important role in physiological signaling, suppression of endogenous oxidants maybe deleterious. Therefore, alternative approaches that can circumvent these limitations are needed. While not previously considered an antioxidant system we propose that the autophagy-lysosomal activities, may serve this essential function in neurodegenerative diseases by removing damaged or dysfunctional proteins and organelles.

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Significant oxidative damage occurs in neurodegenerative disease brains.

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Effective in animal models with single toxins, antioxidants are ineffective in clinical trials.

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The failure of antioxidant therapy maybe due to propagation of cellular damage.

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Autophagic clearance of diverse damaged molecules may provide antioxidant mechanisms.

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Further mechanistic and translational studies on autophagy therapy are needed.

Alleviation of oxidative stress by potent and selective thioredoxin-mimetic peptides

One of the major enzymatic cell defenses providing protection from oxidative injury is the TrxR-Trx system. It consists of NADPH and thioredoxin reductase (TrxR), which maintain thioredoxin (Trx) in a reduced state. Perturbing the TrxR-Trx system with the selective TrxR inhibitor auranofin (AuF; 2,3,4,6-tetra-O-acetyl-1-thio-β-D-glucopyranosato-S-(triethylphosphine) gold) induces oxidative stress by keeping Trx in its oxidized state. We have prepared a family of tri- and tetra-oligopeptides derived from the canonical CxxC motif of the Trx active site and a modified CxC motif. These Trx-mimetic compounds are N- and C-terminal-blocked peptides that consist of two cysteine residues that flank the two-amino-acid CxxC motif (CB4 and CB6) or the single-amino-acid CxC motif (CB3). Catecholamine (CA) secretion in bovine chromaffin cells, which is a highly redox sensitive process, is abolished by AuF. The Trx-mimetic peptides effectively restore CA secretion, as monitored by amperometry in single cells. They also prevent the AuF-induced phosphorylation of p38 mitogen-activated protein kinase (MAPK) and c-Jun NH2-terminal kinase. In PC12 cells, the alleviation of AuF-induced ERK1/2-MAPK phosphorylation by Trx-like peptides parallels their effect of restoring CA secretion. CB3, CB4, and CB6 act intracellularly and are significantly more potent than the traditional antioxidants NAC, GSH, DTT, AD4 (NAC-amide), and ascorbic acid. Taken together, the CxxC and CxC peptides represent a new family of potent and selective redox compounds that could serve as potential candidates for prevention and treatment of oxidative-stress-related disorders.

The biochemical and cellular basis for nutraceutical strategies to attenuate neurodegeneration in Parkinson's disease

Future therapeutic intervention that could effectively decelerate the rate of degeneration within the substantia nigra pars compacta (SNc) could add years of mobility and reduce morbidity associated with Parkinson’s disease (PD). Neurodegenerative decline associated with PD is distinguished by extensive damage to SNc dopaminergic (DAergic) neurons and decay of the striatal tract. While genetic mutations or environmental toxins can precipitate pathology, progressive degenerative succession involves a gradual decline in DA neurotransmission/synaptic uptake, impaired oxidative glucose consumption, a rise in striatal lactate and chronic inflammation. Nutraceuticals play a fundamental role in energy metabolism and signaling transduction pathways that control neurotransmission and inflammation. However, the use of nutritional supplements to slow the progression of PD has met with considerable challenge and has thus far proven unsuccessful. This review re-examines precipitating factors and insults involved in PD and how nutraceuticals can affect each of these biological targets. Discussed are disease dynamics (Sections 1 and 2) and natural substances, vitamins and minerals that could impact disease processes (Section 3). Topics include nutritional influences on α-synuclein aggregation, ubiquitin proteasome function, mTOR signaling/lysosomal-autophagy, energy failure, faulty catecholamine trafficking, DA oxidation, synthesis of toxic DA-quinones, o-semiquinones, benzothiazolines, hyperhomocyseinemia, methylation, inflammation and irreversible oxidation of neuromelanin. In summary, it is clear that future research will be required to consider the multi-faceted nature of this disease and re-examine how and why the use of nutritional multi-vitamin-mineral and plant-based combinations could be used to slow the progression of PD, if possible.

Selenium partially reverses the depletion of striatal dopamine and its metabolites in MPTP-treated C57BL mice

Oxidative stress and inflammation have been implicated in idiopathic Parkinson's disease as well as in the mouse model of this disorder induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Selenium possesses both antioxidant and anti-inflammatory properties; thus we studied the effect of selenium supplementation on MPTP-induced dopaminergic neurotoxicity in mice. C57BL male mice were treated with MPTP (30 mg/kg, i.p.), daily for 4 days. Sodium selenite (Se) was administered in the doses of 0, 1, 2 and 3 mg/kg, 30 min prior to the administration of MPTP. One group of animals served as control (saline only) and another group as Se alone (3 mg/kg). The animals were sacrificed at 24 h after the last dose of MPTP. The striata were isolated and analyzed for dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) levels. Administration of MPTP significantly depleted striatal DA (6.78+/-0.80 microg/g) as compared to control animals (19.32+/-0.77 microg/g) which was significantly prevented by co-treatment with 3 mg/kg dose of Se (12.28+/-0.97 microg/g). MPTP caused significant reduction in striatal DOPAC but the decrease in HVA levels was not significant. Although Se dose-dependently reversed MPTP-induced decreases in DOPAC and HVA levels, these effects were statistically not significant. These findings indicate a significant impairment of dopaminergic neurotransmission by MPTP which is partially reversed by Se treatment.

Glutathione--a review on its role and significance in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease, affecting over a million people in the United States alone, and is characterized by rigidity, bradykinesia, resting tremor, and postural instability. Its main neuropathological feature is the loss of dopaminergic neurons of the substantia nigra pars compacta. However, the pathogenesis of this loss is not understood fully. One of the earliest biochemical changes seen in PD is a reduction in the levels of total glutathione, a key cellular antioxidant. Traditionally, it has been thought that this decrease in GSH levels is the consequence of increased oxidative stress, a process heavily implicated in PD pathogenesis. However, emerging evidence suggests that GSH depletion may itself play an active role in PD pathogenesis. This review aims to explore the contribution of GSH depletion to PD pathogenesis.

Reactive oxygen species production and MAPK activation are implicated in tetrahydrobiopterin-induced SH-SY5Y cell death

Tetrahydrobiopterin (BH4), an obligatory cofactor for dopamine (DA) synthesis, has been shown to produce reactive oxygen species (ROS) upon its autoxidation and induce selective dopaminergic cell death in many in vivo and in vitro models of Parkinson's disease (PD). The precise molecular mechanisms underlying neuronal death upon BH4 exposure, however, have not yet been well elucidated. The present study aims to examine the intracellular ROS production and the signal transduction pathways underlying the toxic effects of BH4 on human dopaminergic SH-SY5Y cells. The results show that BH4 treatment at concentrations ranging from 50microM to 400microM induces neuronal death in a dose-dependent manner. In concomitant with the elevation of intracellular ROS formation, BH4-induced activation of MAPK, p38 and ERK1/2 in SH-SY5Y cells is attenuated by pretreatment with MAPK inhibitors, SB203580 or PD98059. These data indicate that MAPK activation and oxidative stress are involved in BH4-induced dopaminergic cell death, possibly through the autoxidation of BH4 and subsequent ROS production.

Induction of adult human bone marrow mesenchymal stromal cells into functional astrocyte-like cells: potential for restorative treatment in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder with its motor phenomena due mostly to loss of dopamine-producing neurons in the substantia nigra. Pharmacological treatments aimed to increase the deficient dopaminergic neurotransmission are effective in ameliorating the cardinal symptoms, but none of these therapies is curative. It has been suggested that treatment with neurotrophic factors (NTFs) might protect and prevent death of the surviving dopaminergic neurons and induce proliferation of their axonal nerve terminals with reinnervations of the deafferented striatum. However, long-term delivery of such proteins into the CNS is problematic. We therefore aimed to differentiate ex vivo human bone marrow-derived mesenchymal stromal cells into astrocyte-like cells, capable of generating NTFs for future transplantation into basal ganglia of PD patients. Indeed, mesenchymal stromal cells treated with our novel astrocyte differentiation medium, present astrocyte-like morphology and express the astrocyte markers S100beta, glutamine synthetase and glial fibrillary acidic protein. Moreover, these astrocyte-like cells produce and secrete significant amounts of glial cell line-derived neurotrophic factor (GDNF), nerve growth factor (NGF), and brain-derived neurotrophic factor as indicated by messenger RNA, real-time polymerase chain reaction, ELISA, and Western blot analyses. Such NTF-producing cells transplanted into the striatum of 6-hydroxydopamine-lesioned rats, a model of PD, produced a progressive reduction in the apomorphine-induced contralateral rotations as well as behavioral improvement in rotor-rod and the "sunflower seeds" eating motor tests. Histological assessments revealed that the engrafted cells survived and expressed astrocyte and human markers and acted to regenerate the damaged dopaminergic nerve terminal system. Findings indicate that our novel procedure to induce NTF-producing astrocyte-like cells derived from human bone marrow stromal cells might become a promising and feasible autologous transplantation strategy for PD.

Nmnat delays axonal degeneration caused by mitochondrial and oxidative stress

Axonal degeneration is a prominent feature of many neurological disorders that are associated with mitochondrial dysfunction, including Parkinson's disease, motor neuron disease, and inherited peripheral neuropathies. Studies of the Wld(s) mutant mouse, which undergoes delayed Wallerian degeneration in response to axonal injury, suggest that axonal degeneration is an active process. Wld(s) mice also have slower axonal degeneration and disease progression in numerous models of neurodegenerative disease. The Wld(s) mutation results in the production of a chimeric protein that contains the full-length coding sequence of nicotinamide mononucleotide adenylyltransferase 1 (Nmnat1), which alone is sufficient for axonal protection in vitro. To test the effects of increased Nmnat expression on axonal degeneration induced by mitochondrial dysfunction, we examined dorsal root ganglion (DRG) neurons treated with rotenone. Rotenone induced profound axonal degeneration in DRG neurons; however, this degeneration was delayed by expression of Nmnat. Nmnat-mediated protection resulted in decreased axonal accumulation and sensitivity to reactive oxygen species (ROS) but did not affect the change in the rate of rotenone-induced loss in neuronal ATP. Nmnat also prevented axonal degeneration caused by exposure to exogenous oxidants and reduced the level of axonal ROS after treatment with vincristine, further supporting the idea that Nmnat promotes axonal protection by mitigating the effects of ROS.

Endoplasmic reticulum stress and unfolded protein response in Atm-deficient thymocytes and thymic lymphoma cells are attributable to oxidative stress

Both oxidative stress and endoplasmic reticulum (ER) stress have been implicated in carcinogenesis. It is well documented that cells deficient in the ataxia-telangiectasia mutated (ATM) gene undergo oxidative stress, which is critically involved in thymic lymphomagenesis in Atm-/- mice. Here we demonstrate that undifferentiated Atm-/- thymocytes show signs of ER stress and of the unfolded protein response (UPR). Using two-dimensional (2-D) gel electrophoresis and mass spectrometry (MS) analysis, we identified 22 differentially expressed proteins, including the ER stress marker glucose-regulated protein 78 (GRP78), in Atm-/- thymocytes and in Atm-/- thymic lymphoma cells relative to Atm+/+ thymocytes. The phosphorylated alpha subunit of eukaryotic translation initiation factor 2 (p-eIF2alpha), a UPR marker, was also increased in Atm-/- thymocytes. Cells of the ATL-1 line, which were derived from an Atm-/- mouse thymic lymphoma, were more sensitive to the ER stress inducer tunicamycin than were Atm+/+ thymic leukemia ASL-1 cells. Notably, treatment with hydrogen peroxide duplicated the effects of ATM deficiency in cultured thymocytes, and treatment with the novel cell-permeable thiol antioxidant N-acetylcysteine amide (AD4) reduced elevated p-eIF2alpha levels in thymocytes of Atm-/- mice. Thus, we propose that ER stress and the UPR are secondary to oxidative stress in Atm-/- thymocytes.

Melatonin reduces the neuronal loss, downregulation of dopamine transporter, and upregulation of D2 receptor in rotenone-induced parkinsonian rats

Parkinson's disease (PD) is a movement disorder resulting from nigrostriatal dopaminergic neurodegeneration. The impairment of mitochondrial function and dopamine synaptic transmission are involved in the pathogenesis of PD. Two mitochondrial inhibitors, 1-methyl-4-phenylpyridine (MPP(+)) and rotenone, have been used to induce dopaminergic neuronal death both in in vitro and in vivo models of PD. Because the uptake of MPP(+) is mediated by the dopamine transporter (DAT), we used a cell-permeable rotenone-induced PD model to investigate the role of DAT and dopamine D2 receptor (D2R) on dopaminergic neuronal loss. Rotenone subcutaneously infused for 14 days induced PD symptoms in rats, as indicated by reduced spontaneous locomotor activity (hypokinesis), loss of tyrosine hydroxylase (TH, a marker enzyme for dopamine neurons) immunoreactivity in the substantia nigra and striatum, obvious alpha-synuclein accumulation, downregulated DAT protein expression, and upregulated D2R expression. Interestingly, rotenone also caused significant noradrenergic neuronal loss in the locus coeruleus. Melatonin, an antioxidant, prevented nigrostriatal neurodegeneration and alpha-synuclein aggregation without affecting the rotenone-induced weight loss and hypokinesis. However, rotenone-induced hypokinesis was markedly reversed by the DAT antagonist nomifensine and body weight loss was attenuated by the D2R antagonist sulpiride. In addition, both antagonists significantly prevented the reduction of striatal TH or DAT immunoreactivity but not the loss of nigral TH- and DAT-immunopositive neurons. These results suggested that oxidative stress and DAT downregulation are involved in the rotenone-induced pathogenesis of nigrostriatal dopaminergic neurodegeneration, whereas D2R upregulation may simply represent a compensatory response.

Modulation of peroxisome proliferator-activated receptor-alpha activity by N-acetyl cysteine attenuates inhibition of oligodendrocyte development in lipopolysaccharide stimulated mixed glial cultures

Glial cells secrete proinflammatory mediators in the brain in response to exogenous stimuli such as infection and injury. Previously, we documented that systemic maternal lipopolysaccharide (LPS)-exposure at embryonic gestation day 18 causes oligodendrocyte (OL)-injury/hypomyelination in the developing brain which can be attenuated by N-acetyl cysteine (NAC; precursor of glutathione). The present study delineates the underlying mechanism of NAC-mediated attenuation of inhibition of OL development in LPS-stimulated mixed glial cultures. Factors released by LPS-stimulated mixed glial cultures inhibited OL development as shown by decrease in both proliferation 3bromo-deoxyuridine+/chondroitin sulfate proteoglycan-NG2+, hereafter BrdU+/NG+ and differentiation (O4+ and myelin basic protein+) of OL-progenitors. Correspondingly, an impairment of peroxisomal proliferation was shown by a decrease in the level of peroxisomal proteins in the developing OLs following exposure to LPS-conditioned media (LCM). Both NAC and WY14643, a peroxisome proliferator-activated receptor (PPAR)-alpha agonist attenuated these LCM-induced effects in OL-progenitors. Similar to WY14643, NAC attenuated LCM-induced inhibition of PPAR-alpha activity in developing OLs. Studies conducted with cytokines and diamide (a thiol-depleting agent) confirmed that cytokines are active agents in LCM which may be responsible for inhibition of OL development via peroxisomal dysfunction and induction of oxidative stress. These findings were further corroborated by similar treatment of developing OLs generated from PPAR-alpha(-/-) and wild-type mice or B12 oligodendroglial cells co-transfected with PPAR-alpha small interfering RNAs/pTK-PPREx3-Luc plasmids. Collectively, these data provide evidence that the modulation of PPAR-alpha activity, thus peroxisomal function by NAC attenuates LPS-induced glial factors-mediated inhibition of OL development suggesting new therapeutic interventions to prevent the devastating effects of maternal infections.

Unconjugated bilirubin differentially affects the redox status of neuronal and astroglial cells

We investigated whether nerve cell damage by unconjugated bilirubin (UCB) is mediated by oxidative stress and ascertained the neuronal and astroglial susceptibility to injury. Several oxidative stress biomarkers and cell death were determined following incubation of neurons and astrocytes isolated from rat cortical cerebrum with UCB (0.01-1.0 microM). We show that UCB induces a dose-dependent increase in neuronal death in parallel with the oxidation of cell components and a decrease in the intracellular glutathione content. Comparison of the results obtained in both cell types demonstrates that neurons are more vulnerable than astrocytes to oxidative injury by UCB, for which accounts the lower glutathione stores in neuronal cells. Moreover, neuronal oxidative injury is prevented by supplementation with N-acetylcysteine, a glutathione precursor, whereas astroglial sensitivity to UCB is enhanced by inhibition of glutathione synthesis, using buthionine sulfoximine. Collectively, we demonstrate that oxidative stress is involved in UCB neurotoxicity and depict a new therapeutic approach for UCB-induced oxidative damage.

Lipopolysaccharide-induced peroxisomal dysfunction exacerbates cerebral white matter injury: attenuation by N-acetyl cysteine

Cerebral white matter injury during prenatal maternal infection characterized as periventricular leukomalacia is the main substrate for cerebral palsy (CP) in premature infants. Previously, we reported that maternal LPS exposure causes oligodendrocyte (OL)-injury/hypomyelination in the developing brain which can be attenuated by an antioxidant agent, N-acetyl cysteine (NAC). Herein, we elucidated the role of peroxisomes in LPS-induced neuroinflammation and cerebral white matter injury. Peroxisomes are important for detoxification of reactive oxidative species (ROS) and metabolism of myelin-lipids in OLs. Maternal LPS exposure induced selective depletion of developing OLs in the fetal brain which was associated with ROS generation, glutathione depletion and peroxisomal dysfunction. Likewise, hypomyelination in the postnatal brain was associated with decrease in peroxisomes and OLs after maternal LPS exposure. Conversely, NAC abolished these LPS-induced effects in the developing brain. CP brains imitated these observed changes in peroxisomal/myelin proteins in the postnatal brain after maternal LPS exposure. In vitro studies revealed that pro-inflammatory cytokines cause OL-injury via peroxisomal dysfunction and ROS generation. NAC or WY14643 (peroxisome proliferators activated receptor (PPAR)-alpha agonist) reverses these effects of pro-inflammatory cytokines in the wild-type OLs, but not in PPAR-alpha(-/-) OLs. Similarly treated B12 oligodenroglial cells co-transfected with PPAR-alpha siRNAs/pTK-PPREx3-Luc, and LPS exposed PPAR-alpha(-/-) pregnant mice treated with NAC or WY14643 further suggested that PPAR-alpha activity mediates NAC-induced protective effects. Collectively, these data provide unprecedented evidence that LPS-induced peroxisomal dysfunction exacerbates cerebral white matter injury and its attenuation by NAC via a PPAR-alpha dependent mechanism expands therapeutic avenues for CP and related demyelinating diseases.

N-acetylcysteine amide (AD4) attenuates oxidative stress in beta-thalassemia blood cells

Many aspects of the pathology in beta-hemoglobinopathies (beta-thalassemia and sickle cell anemia) are mediated by oxidative stress. In the present study we tested a novel thiol compound, N-acetylcysteine amide (AD4), the amide form of N-acetyl cysteine (NAC) for its antioxidant effects. Using flow-cytometry, we showed that in vitro treatment of blood cells from beta-thalassemic patients with AD4 elevated the reduced glutathione (GSH) content of red blood cells (RBC), platelets and polymorphonuclear (PMN) leukocytes, and reduced their ROS. These effects resulted in a significant reduced sensitivity of thalassemic RBC to hemolysis and phagocytosis by macrophages. Intra-peritoneal injection of AD4 to beta-thalassemic mice (150 mg/kg) reduced the parameters of oxidative stress (p<0.001). Our results show the superiority of AD4, compared to NAC, in reducing oxidative stress markers in thalassemic cells both in vitro and in vivo.

1-methyl-4-phenylpyridinium-induced alterations of glutathione status in immortalized rat dopaminergic neurons

Decreased glutathione levels associated with increased oxidative stress are a hallmark of numerous neurodegenerative diseases, including Parkinson's disease. GSH is an important molecule that serves as an anti-oxidant and is also a major determinant of cellular redox environment. Previous studies have demonstrated that neurotoxins can cause changes in reduced and oxidized GSH levels; however, information regarding steady state levels remains unexplored. The goal of this study was to characterize changes in cellular GSH levels and its regulatory enzymes in a dopaminergic cell line (N27) following treatment with the Parkinsonian toxin, 1-methyl-4-phenylpyridinium (MPP(+)). Cellular GSH levels were initially significantly decreased 12 h after treatment, but subsequently recovered to values greater than controls by 24 h. However, oxidized glutathione (GSSG) levels were increased 24 h following treatment, concomitant with a decrease in GSH/GSSG ratio prior to cell death. In accordance with these changes, ROS levels were also increased, confirming the presence of oxidative stress. Decreased enzymatic activities of glutathione reductase and glutamate-cysteine ligase by 20-25% were observed at early time points and partly account for changes in GSH levels after MPP(+) exposure. Additionally, glutathione peroxidase activity was increased 24 h following treatment. MPP(+) treatment was not associated with increased efflux of glutathione to the medium. These data further elucidate the mechanisms underlying GSH depletion in response to the Parkinsonian toxin, MPP(+).

Perturbed Synaptosomal Calcium Homeostasis and Behavioral Deficits Following Carbofuran Exposure: Neuroprotection by N-Acetylcysteine

The protective effects of N-acetylcysteine (NAC) on carbofuran-induced alterations in calcium homeostasis and neurobehavioral functions were investigated in rats. Rats were exposed to carbofuran at a dose of 1 mg/kg body weight, orally for a period of 28 days. A significant decrease in Ca2+ATPase activity was observed following carbofuran exposure with a concomitant increase in K+ -induced (45)Ca2+ uptake through voltage operated calcium channels. This was accompanied with a marked accumulation of intracellular free calcium in synaptosomes. The increase in intracellular calcium levels were associated with an increased lipid peroxidation and decreased glutathione content in carbofuran exposed animals. NAC administration (200 mg/kg body weight, orally) to the carbofuran exposed animals had a beneficial effect on carbofuran-induced alterations in calcium homeostasis and resulted in repletion in glutathione levels and resulted in lowering the extent of lipid peroxidation. Marked impairment in the motor functions were seen following carbofuran exposure, which were evident by the significant decrease in the locomotor activity and reduction in the retention time of the rats on rotating rods. Cognitive deficits were also seen as indicated by the significant decrease in active and passive avoidance response. NAC treatment, on the other hand, protected the animals against carbofuran-induced neurobehavioral deficits. The results support the hypothesis that carbofuran exerts its toxic effects by disrupting calcium homeostasis, which may have serious consequences on neuronal functioning, and clearly show the potential beneficial effects of N-acetylcysteine on carbofuran induced alterations in synaptosomal calcium homeostasis.

Oxidative stress and therapeutic approaches in HIV dementia

Despite the rapidly increasing incidence of HIV infection worldwide and the increasing prevalence of HIVassociated cognitive impairment, even in patients adequately treated with antiretroviral therapy, currently no effective treatment exists for HIV dementia. A broad range of studies using either brain or cerebrospinal fluid (CSF) tissues from well-characterized patients with HIV dementia, animal models, and in vitro studies from several laboratories using HIV-infected cells or HIV proteins provide overwhelming evidence for oxidative stress in mediating neuronal injury in this patient population. These studies also suggest that patients with apolipoprotein E (ApoE) 4 allele are more susceptible to such oxidative damage. In this review, we provide a critical analysis of these studies, including the few clinical trials that have used antioxidants to treat HIV dementia. We also discuss several novel agents with potent antioxidative properties and provide a rationale for combination antioxidant and neuroprotective therapy.

In vitro and in vivo neuroprotection by γ-glutamylcysteine ethyl ester against MPTP: Relevance to the role of glutathione in Parkinson's disease

Glutathione is an abundant intracellular thiol antioxidant whose levels are reduced both in Parkinson's disease itself and in a widely used animal model of the disorder, systemic MPTP administration. Previous in vitro work from our laboratory has suggested that glutathione depletion may be directly responsible for mitochondrial dysfunction, which ultimately leads to dopaminergic cell death associated with the disease. Here, we demonstrate the ability of gamma-glutamylcysteine ethyl ester, a lipid permeable derivative of the major substrate for scavenger glutathione synthesis, to counteract glutathione loss and neurodegeneration associated with in vitro and in vivo administration of MPTP or its derivatives. This data suggests that prevention of glutathione depletion is a likely therapeutic target for the disease.

Quebrachitol (2-O-methyl-L-inositol) attenuates 6-hydroxydopamine-induced cytotoxicity in rat fetal mesencephalic cell cultures

Naturally occurring plant substances have the potential to prevent oxidative damage in various pathophysiological conditions including neurodegenerative disorders. Recent findings indicate that impaired energy metabolism plays a prominent role in neurodegeneration. The present study investigated whether quebrachitol (2-O-methyl-L-inositol) (QCT), a sugar like natural compound that was suggested to have both antioxidant and membrane stabilization activity prevents the cytotoxic effect of 6-hydroxydopamine (6-OHDA, 200 microM) on cultured rat fetal mesencephalic cells. While QCT (0.1-100 microg/ml) produced no effect per se on cell viability as measured in the 3[4,5-dimethylthiazole-2il]-2,5-diphenyltetrazolium bromide (MTT) test, it offered concentration-related protection against cell death induced by 6-OHDA. In addition, QCT demonstrated an antioxidant activity against 6-OHDA-induced oxidative stress as evidenced by reduced formation of nitrite-nitrate and thiobarbituric acid-related substances. Fluorescence microscopy using acridine orange/ethidium bromide double staining further affirmed the absence of 6-OHDA (200 microM)-induced morphological changes characteristic of apoptosis/necrosis in cultures pretreated with QCT (100 microg/ml). Also, results of tyrosine hydroxylase immunoreactivity indicated that 6-OHDA induces cell death in mesencephalic cultures affecting both TH+ positive and TH- negative (TH+ and TH-, respectively) and QCT pretreatment protects them from cell death, in a non-specific manner. Our data indicate that QCT has a cytoprotective role due, at least in part, to an antioxidant and free radical scavenging mechanism. Furthermore, the study suggests that inositol compounds might serve as leads in developing drugs for the treatment of various neurodegenerative disorders.

A novel brain-targeted antioxidant (AD4) attenuates haloperidol-induced abnormal movement in rats: implications for tardive dyskinesia

BACKGROUND

Tardive dyskinesia (TD), characterized by abnormal movements, is the major late-onset chronic side effect of antipsychotic treatment found in about 30% of those patients. The association of oxidative stress and the release of free radicals is one of the hallmarks of dopaminergic malfunctions and is one of the leading theories suggested for the pathophysiology of TD. To this day, no brain-targeted antioxidant has been tested as a potential treatment of TD. In light of this assumption, the authors chose a novel, low-molecular weight thiol antioxidant, N-acetyl cysteine amide (AD4), that crosses the blood-brain barrier as a possible treatment of TD.

OBJECTIVE

To examine the protective effects of the novel brain-penetrating antioxidant AD4 on TD experimental models.

METHODS

The typical vacuous chewing movement occurs in rats following chronic haloperidol injections (1.5 mg/kg/day intraperitoneally for 21 days). This purposeless mouth opening in the vertical plane is similar to TD symptoms in humans. The authors tested rats treated with haloperidol without or with AD4 in the drinking water (1 g/kg orally). Thiobarbituric acid reactive substances and anticarbonyl antibodies were used to measure oxidation of membranes and proteins.

RESULTS

Haloperidol increased the vacuous chewing movements to 66.5 +/- 7.6 movements/5 minutes compared with 16.4 +/- 2.4 movements/5 minutes in untreated rats (P < 0.01). Coadministration of haloperidol and AD4 decreased the vacuous chewing movements level to 42.1 +/- 6.7 movements/5 minutes (P < 0.05). Haloperidol also increased the level of lipid peroxidation and protein oxidation in the rat brain, whereas coadministration with AD4 preserved their normal levels.

CONCLUSION

Haloperidol causes behavioral abnormalities associated with oxidative stress in rats, similar to TD. AD4, the brain-targeted potent antioxidant, reduces the cellular oxidation markers and improves the typical clinical behavior. Hence, AD4 is a potential new treatment of antipsychotic-induced TD.

Low molecular weight thiol amides attenuate MAPK activity and protect primary neurons from Abeta(1-42) toxicity

Oxidative stress caused by various stimuli lead to oxidation of glutathione (GSH), the major redox power of the cell. Amyloid beta [Abeta(1-42)] is one of the key components of senile plaques and is involved in the progress initiation and triggers of Alzheimer's disease (AD). Lower GSH levels correlated with the activation of mitogen-activated proteins kinases (MAPK) have been demonstrated in AD, Parkinson's disease (PD) and other neurodegenerative disorders and have been proposed to play a central role in the deterioration of the aging and neurodegenerative brain. In this study, we evaluated the ability of low molecular weight thiol amides, N-acetyl cysteine amide (AD4) that replenishes GSH levels, N-acetyl glycine cysteine amide (AD7) and N-acetyl-Cys-Gly-Pro-Cys-amide (CB4) to protect primary neuronal culture against the oxidative and neurotoxic effects of Abeta(1-42) and to inhibit cisplatin- and hydrogen-peroxide-induced phosphorylation of two MAP kinases (MAPK), p38 and ERK1/2, in NIH3T3 cells. Cell death induced by Abeta(1-42) in primary neuronal cells was reversed by the thiol amides. Likewise, protein oxidation, loss of mitochondrial function and DNA fragmentation all returned to control levels by pretreatment with the three thiol amides. Elevated phosphorylation of ERK1/2 and p38 induced by cisplatin or H2O2 in NIH3T3 cells was lowered by AD4, AD7 and CB4 in a dose-dependent manner. Taken together, these results suggest that the thiol amides AD4, AD7 and CB4 protect neuronal cells against Abeta(1-42) toxicity by attenuating oxidative stress in correlation with inhibiting the MAPK phosphorylation cascade. These results are consistent with the notion that these small molecular thiol amides may play a viable protective role in the oxidative and neurotoxicity induced by Abeta(1-42) in AD brain.

Microglia and inflammation-mediated neurodegeneration: multiple triggers with a common mechanism

Inflammation, a common denominator among the diverse list of neurodegenerative diseases, has recently been implicated as a critical mechanism responsible for the progressive nature of neurodegeneration. Microglia are the resident innate immune cells in the central nervous system and produce a barrage of factors (IL-1, TNFalpha, NO, PGE2, superoxide) that are toxic to neurons. Evidence supports that the unregulated activation of microglia in response to environmental toxins, endogenous proteins, and neuronal death results in the production of toxic factors that propagate neuronal injury. In the following review, we discuss the common thread of microglial activation across numerous neurodegenerative diseases, define current perceptions of how microglia are damaging neurons, and explain how the microglial response to neuronal damage results in a self-propelling cycle of neuron death.