Oxidative stress and neuronal DNA fragmentation mediate age-dependent vulnerability to the mitochondrial toxin, 3-nitropropionic acid, in the mouse striatum

Integrative analysis of transcriptomic and metabolomic profiles reveals abnormal phosphatidylinositol metabolism in follicles from endometriosis‐associated infertility patients

Endometriosis is a common gynecological disorder that causes female infertility. Our recent research found that excessive oxidative stress in ovaries of endometriosis patients induced senescence of cumulus granulosa cells. Here, we analyzed the transcriptomic and metabolomics profiles of follicles in a mouse model of endometriosis and in patients with endometriosis and investigated the potential function of changed metabolites in granulosa cells. RNA-sequencing indicated that both endometriosis lesions and oxidative stress in mice induced abnormalities of reactive oxidative stress, steroid hormone biosynthesis, and lipid metabolism. The mouse model and women with endometriosis showed altered lipid metabolism. Nontargeted metabolite profiling of follicular fluid from endometriosis and male-factor infertility patients by liquid chromatography mass spectrometry identified 55 upregulated and 67 downregulated metabolites. These differential metabolites were mainly involved in steroid hormone biosynthesis and glycerophospholipid metabolism. Phosphatidylinositol (PI 16:0/18:2) was significantly elevated in follicular fluid from endometriosis patients compared with controls (p < 0.05), while lysophosphatidylinositol (LPI 18:2, 20:2, 18:1, 20:3 and 18:3) was reduced (p < 0.05). Upregulated PI and downregulated LPI correlated with oocyte retrieval number and mature oocyte number. LPI inhibited cellular reactive oxidative stress induced by hemin in granulosa cells. Cell proliferation inhibition, senescence, and apoptosis induced by hemin were partially reversed by LPI. Moreover, LPI administration rescued hemin blocking of cumulus-oocyte complex expansion and stimulated expression of ovulation-related genes. Transcriptomic Switching mechanism at 5' end of the RNA transcript sequencing and western blot revealed that LPI effects on granulosa cells were associated with its regulation of MAPK-ERK1/2 signaling, which was suppressed in the presence of hemin. In conclusion, our results revealed the dysregulation of lipid metabolism in endometriotic follicles. LPI may represent a novel agent for in vitro follicular culture that reverses the excessive oxidative stress from endometriotic lesions. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Ageing and the Autonomic Nervous System

The vertebrate nervous system is divided into central (CNS) and peripheral (PNS) components. In turn, the PNS is divided into the autonomic (ANS) and enteric (ENS) nervous systems. Ageing implicates time-related changes to anatomy and physiology in reducing organismal fitness. In the case of the CNS, there exists substantial experimental evidence of the effects of age on individual neuronal and glial function. Although many such changes have yet to be experimentally observed in the PNS, there is considerable evidence of the role of ageing in the decline of ANS function over time. As such, this chapter will argue that the ANS constitutes a paradigm for the physiological consequences of ageing, as well as for their clinical implications.

Cross-species metabolomic analysis of tau- and DDT-related toxicity

Exposure to the pesticide dichlorodiphenyltrichloroethane (DDT) has been associated with increased risk of Alzheimer's disease (AD), a disease also associated with hyperphosphorylated tau (p-tau) protein aggregation. We investigated whether exposure to DDT can exacerbate tau protein toxicity in Caenorhabditiselegans using a transgenic strain that expresses human tau protein prone to aggregation by measuring changes in size, swim behavior, respiration, lifespan, learning, and metabolism. In addition, we examined the association between cerebrospinal fluid (CSF) p-tau protein-as a marker of postmortem tau burden-and global metabolism in both a human population study and in C. elegans, using the same p-tau transgenic strain. From the human population study, plasma and CSF-derived metabolic features associated with p-tau levels were related to drug, amino acid, fatty acid, and mitochondrial metabolism pathways. A total of five metabolites overlapped between plasma and C. elegans, and four between CSF and C. elegans. DDT exacerbated the inhibitory effect of p-tau protein on growth and basal respiration. In the presence of p-tau protein, DDT induced more curling and was associated with reduced levels of amino acids but increased levels of uric acid and adenosylselenohomocysteine. Our findings in C. elegans indicate that DDT exposure and p-tau aggregation both inhibit mitochondrial function and DDT exposure can exacerbate the mitochondrial inhibitory effects of p-tau aggregation. Further, biological pathways associated with exposure to DDT and p-tau protein appear to be conserved between species.

Directly Reprogrammed Human Neurons to Understand Age-Related Energy Metabolism Impairment and Mitochondrial Dysfunction in Healthy Aging and Neurodegeneration

Brain aging is characterized by several molecular and cellular changes grouped as the hallmarks or pillars of aging, including organelle dysfunction, metabolic and nutrition-sensor changes, stem cell attrition, and macromolecular damages. Separately and collectively, these features degrade the most critical neuronal function: transmission of information in the brain. It is widely accepted that aging is the leading risk factor contributing to the onset of the most prevalent pathological conditions that affect brain functions, such as Alzheimer's, Parkinson's, and Huntington's disease. One of the limitations in understanding the molecular mechanisms involved in those diseases is the lack of an appropriate cellular model that recapitulates the “aged” context in human neurons. The advent of the cellular reprogramming of somatic cells, i.e., dermal fibroblasts, to obtain directly induced neurons (iNs) and induced pluripotent stem cell- (iPSC-) derived neurons is technical sound advances that could open the avenues to understand better the contribution of aging toward neurodegeneration. In this review, we will summarize the commonalities and singularities of these two approaches for the study of brain aging, with an emphasis on the role of mitochondrial dysfunction and redox biology. We will address the evidence showing that iNs retain age-related features in contrast to iPSC-derived neurons that lose the aging signatures during the reprogramming to pluripotency, rendering iNs a powerful strategy to deepen our knowledge of the processes driving normal cellular function decline and neurodegeneration in a human adult model. We will finally discuss the potential utilization of these novel technologies to understand the differential contribution of genetic and epigenetic factors toward neuronal aging, to identify and develop new drugs and therapeutic strategies.

Withania somnifera (L.) Dunal (Ashwagandha): A comprehensive review on ethnopharmacology, pharmacotherapeutics, biomedicinal and toxicological aspects

Withania somnifera (L.) Dunal (Solanaceae) has been used as a traditional Rasayana herb for a long time. Traditional uses of this plant indicate its ameliorative properties against a plethora of human medical conditions, viz. hypertension, stress, diabetes, asthma, cancer etc. This review presents a comprehensive summary of the geographical distribution, traditional use, phytochemistry, and pharmacological activities of W. somnifera and its active constituents. In addition, it presents a detailed account of its presence as an active constituent in many commercial preparations with curative properties and health benefits. Clinical studies and toxicological considerations of its extracts and constituents are also elucidated. Comparative analysis of relevant in-vitro, in-vivo, and clinical investigations indicated potent bioactivity of W. somnifera extracts and phytochemicals as anti-cancer, anti-inflammatory, apoptotic, immunomodulatory, antimicrobial, anti-diabetic, hepatoprotective, hypoglycaemic, hypolipidemic, cardio-protective and spermatogenic agents. W. somnifera was found to be especially active against many neurological and psychological conditions like Parkinson's disease, Alzheimer's disease, Huntington's disease, ischemic stroke, sleep deprivation, amyotrophic lateral sclerosis, attention deficit hyperactivity disorder, bipolar disorder, anxiety, depression, schizophrenia and obsessive-compulsive disorder. The probable mechanism of action that imparts the pharmacological potential has also been explored. However, in-depth studies are needed on the clinical use of W. somnifera against human diseases. Besides, detailed toxicological analysis is also to be performed for its safe and efficacious use in preclinical and clinical studies and as a health-promoting herb.

Molecular and cellular pathways contributing to brain aging

Aging is the leading risk factor for several age-associated diseases such as neurodegenerative diseases. Understanding the biology of aging mechanisms is essential to the pursuit of brain health. In this regard, brain aging is defined by a gradual decrease in neurophysiological functions, impaired adaptive neuroplasticity, dysregulation of neuronal Ca2+ homeostasis, neuroinflammation, and oxidatively modified molecules and organelles. Numerous pathways lead to brain aging, including increased oxidative stress, inflammation, disturbances in energy metabolism such as deregulated autophagy, mitochondrial dysfunction, and IGF-1, mTOR, ROS, AMPK, SIRTs, and p53 as central modulators of the metabolic control, connecting aging to the pathways, which lead to neurodegenerative disorders. Also, calorie restriction (CR), physical exercise, and mental activities can extend lifespan and increase nervous system resistance to age-associated neurodegenerative diseases. The neuroprotective effect of CR involves increased protection against ROS generation, maintenance of cellular Ca2+ homeostasis, and inhibition of apoptosis. The recent evidence about the modem molecular and cellular methods in neurobiology to brain aging is exhibiting a significant potential in brain cells for adaptation to aging and resistance to neurodegenerative disorders.

In Pursuit of Healthy Aging: Effects of Nutrition on Brain Function

Consuming a balanced, nutritious diet is important for maintaining health, especially as individuals age. Several studies suggest that consuming a diet rich in antioxidants and anti-inflammatory components such as those found in fruits, nuts, vegetables, and fish may reduce age-related cognitive decline and the risk of developing various neurodegenerative diseases. Numerous studies have been published over the last decade focusing on nutrition and how this impacts health. The main objective of the current article is to review the data linking the role of diet and nutrition with aging and age-related cognitive decline. Specifically, we discuss the roles of micronutrients and macronutrients and provide an overview of how the gut microbiota-gut-brain axis and nutrition impact brain function in general and cognitive processes in particular during aging. We propose that dietary interventions designed to optimize the levels of macro and micronutrients and maximize the functioning of the microbiota-gut-brain axis can be of therapeutic value for improving cognitive functioning, particularly during aging.

Proteotoxicity and mitochondrial dynamics in aging diabetic brain

Impaired neuronal proteostasis is a salient feature of both aging and protein misfolding disorders. Amyloidosis, a consequence of this phenomena is observed in the brains of diabetic patients over the chronic time period. These toxic aggregates not only cause age-related decline in proteostasis, but also dwindle its ability to increase or restore the chaperones in response to any stressful condition. Mitochondria acts as the main source of energy regulation and many metabolic disorders such as diabetes have been associated with altered oxidative phosphorylation (OxPhos) and redox imbalance in the mitochondria. The mitochondrial unfolded protein response (UPR^mt) acts as a mediator for maintaining the mitochondrial protein homeostasis and quality control during such conditions. Over a long time period, these responses start shutting off leading to proteotoxic stress in the neurons. This reduces the buffering capacity of protein network signalling during aging, thereby increasing the risk of neurodegeneration in the brain. In this review, we focus on the proteotoxic stress that occurs as an amalgamation of diabetes and aging, as well as the impact of mitochondrial dysfunction on the neuronal survival affecting the diabetic brain and its long term consequences on the memory changes.

Excessive oxidative stress in cumulus granulosa cells induced cell senescence contributes to endometriosis-associated infertility

Endometriosis an important cause of female infertility and seriously impact physical and psychological health of patients. Endometriosis is now considered to be a public health problem that deserves in-depth investigation, especially the etiopathogenesis of endometriosis-associated infertility. We aimed to illuminate the etiopathogenesis of endometriosis-associated infertility that involve excessive oxidative stress (OS) induced pathological changes of ovary cumulus granulosa cell (GCs). Senescence-associated β-galactosidase (SA β-gal) activity in GCs from endometriosis patients, soluble isoform of advanced glycation end products receptor (sRAGE) expression in follicular fluid from endometriosis patients and differentially expressed senescence-associated secretory phenotype factors (IL-1β, MMP-9, KGF and FGF basic protein) are all useful indexes to evaluate oocyte retrieval number and mature oocyte number. RNA-sequencing and bioinformatics analysis indicated senescent phenotype of endometriosis GCs and aggravated endoplasmic reticulum (ER) stress in endometriosis GCs. Targeting ER stress significantly alleviated OS-induced GCs senescence as well as mitochondrial membrane potential (MMP) and adenosine triphosphate (ATP) reduction in GCs. Moreover, melatonin administration rescued OS-enhanced ER stress, cellular senescence, and MMP and ATP abnormities of endometriosis GCs in vitro and in vivo. In conclusion, our results indicated excessive reactive oxygen species induces senescence of endometriosis GCs via arouse ER stress, which finally contributes to endometriosis-associated infertility, and melatonin may represent a novel adjuvant therapy strategy for endometriosis-associated infertility.

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Endometriosis patients ovary cumulus granulosa cells (GCs) show senescence phenotype.

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Excessive oxidative stress in GCs drives cellular senescence via activating ER stress.

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Melatonin alleviates ER stress and GCs senescence in vitro and in vivo.

Hallmarks of Brain Aging: Adaptive and Pathological Modification by Metabolic States

During aging, the cellular milieu of the brain exhibits tell-tale signs of compromised bioenergetics, impaired adaptive neuroplasticity and resilience, aberrant neuronal network activity, dysregulation of neuronal Ca2+ homeostasis, the accrual of oxidatively modified molecules and organelles, and inflammation. These alterations render the aging brain vulnerable to Alzheimer's and Parkinson's diseases and stroke. Emerging findings are revealing mechanisms by which sedentary overindulgent lifestyles accelerate brain aging, whereas lifestyles that include intermittent bioenergetic challenges (exercise, fasting, and intellectual challenges) foster healthy brain aging. Here we provide an overview of the cellular and molecular biology of brain aging, how those processes interface with disease-specific neurodegenerative pathways, and how metabolic states influence brain health.

Characterization of age-dependent changes in the striatum: Response to the mitochondrial toxin 3-nitropropionic acid

Neurodegenerative phenomena are associated with mitochondrial dysfunction and this could be exacerbated by aging. Age-dependence of mitochondrial response to toxins could help understand these mechanisms and evolve novel therapeutics. 3-Nitropropionic acid (3-NPA) is a mitochondrial toxin that induces neurotoxicity in the striatum via inhibition of complex II. We investigated the age-related events that contribute to 3-NPA toxicity. 3-NPA induced neuronal death, oxidative stress and altered mitochondrial structure in neuronal cells. 3-NPA injection in vivo caused motor impairment, mitochondrial dysfunction and oxidative damage with different trend in young and adult mice. To understand the age-dependent mechanisms, we carried out proteomic analysis of the striatal protein extract from young mice (control: YC vs. 3-NPA treated: YT) and adult mice (control: AC vs. 3-NPA treated: AT). Among the 3752 identified proteins, 33 differentially expressed proteins (mitochondrial, synaptic and microsomal proteins) were unique either to YT or AT. Interestingly, comparison of the proteomic profile in AC and YC indicated that 161 proteins (linked with cytoskeletal structure, neuronal development, axogenesis, protein transport, cell adhesion and synaptic function) were down-regulated in AC compared to YC. We surmise that aging contributes to the cellular and molecular architecture in the mouse striatum with implications for neurodegeneration.

Effect of methotrexate exposure at late gestation on development of telencephalon in rat fetal brain

Pregnant rats were treated with 30 mg/kg of methotrexate (MTX) on gestation day (GD) 16, and fetal brains were examined time-dependently. On GD 20, the appearance of the telencephalon in the MTX group was different from that in the control group, and the major axis of the telencephalon of the MTX group was shortened, compared to that of the control group. In the sagittal section of the telencephalon in the MTX group on GD 20, histopathological findings of deformation and narrowing of the cerebral ventricle, the disturbance of the arrangement of the marginal cell layer of subventricular zone (SVZ) and thickening of telencephalic wall, cortical plate and ventricular zone (VZ)/SVZ were possibly attributable to neuronal migration disorders by MTX. Through all the experimental period, few pyknotic cells or TUNEL-positive cells were observed in the VZ/SVZ of the telencephalic wall and striatum in the control group. On the other hand, in the VZ/SVZ of the telencephalic wall and striatum in the MTX group, pyknotic cells or TUNEL-positive cells were observed on GD 17, and they increased significantly on GD18 and then decreased to the control levels from GD 19 onward. The phospho-Histone H3-positive rate decreased remarkedly in the VZ/SVZ of the telencephalic wall and striatum of the MTX group on GDs 17 and 18, compared to the control group, but they recovered on and after GD 19. These results suggested that there was a high possibility that development of the telencephalon in this period required strong folic acid.

mRNA expression levels of PGC-1α in a transgenic and a toxin model of Huntington's disease

Peroxisome proliferator-activated receptor-gamma (PPARγ) coactivator-1 alpha (PGC-1α) is involved in the regulation of mitochondrial biogenesis, respiration, and adaptive thermogenesis. The full-length PGC-1α (FL-PGC-1α) comprises multiple functional domains interacting with several transcriptional regulatory factors such as nuclear respiratory factors, estrogen-related receptors, and PPARs; however, a number of PGC-1α splice variants have also been reported recently. In this study, we examined the expression levels of FL-PGC-1α and N-truncated PGC-1α (NT-PGC-1α), a shorter but functionally active splice variant of PGC-1α protein, in N171-82Q transgenic and 3-nitropropionic acid-induced murine model of Huntington's disease (HD). The expression levels were determined by RT-PCR in three brain areas (striatum, cortex, and cerebellum) in three age groups (8, 12, and 16 weeks). Besides recapitulating prior findings that NT-PGC-1α is preferentially increased in 16 weeks of age in transgenic HD animals, we detected age-dependent alterations in both models, including a cerebellum-predominant upregulation of both PGC-1α variants in transgenic mice, and a striatum-predominant upregulation of both PGC-1α variants after acute 3-nitropropionic acid intoxication. The possible relevance of this expression pattern is discussed. Based on our results, we assume that increased expression of PGC-1α may serve as a compensatory mechanism in response to mitochondrial damage in transgenic and toxin models of HD, which may be of therapeutic relevance.

Do glial cells play an anti-oxidative role in Huntington's disease?

Oxidative stress is a condition of imbalance between reactive oxygen species (ROS) formation and antioxidant capacity as a result of dysfunction of the antioxidant system. ROS can be served as a second messenger at low or moderate concentration, while excessive amount of ROS under oxidative stress condition would destroy macromolecules like proteins, DNA, and lipids, finally leading to cell apoptosis or necrosis. Changes in these macromolecules are involved in various pathological changes and progression of diseases, especially neurodegenerative diseases. Neurodegenerative diseases are morphologically featured by progressive neuronal cell loss, accompanied with inclusions formed by protein aggregates in neurons or glial cells. Neurons have always received much more attention than glial cells in neurodegenerative diseases. Actually, glial cells might play a key role in the functioning of neurons and cellular survival through an antioxidant way. Additionally, neurons can modulate the activities of glia either. Herein, the main purposes of this review are to mention the connection between Huntington's disease (HD) and oxidative stress, to summarize the characteristics and functions of glial cells in HD, to state the cross talk between neurons and glial cells, and to emphasize the conclusive role of activation of Keap1-Nrf2-ARE pathway in glial cells against oxidative stress in HD.

Apoptosis signal-regulating kinase-1 aggravates ROS-mediated striatal degeneration in 3-nitropropionic acid-infused mice

Apoptosis signal-regulating kinase-1 (ASK1), an early signaling element in the cell death pathway, has been suggested to participate in the pathology of neurodegenerative diseases, which may be associated with environmental factors that impact the diseases. Although it is not entirely elucidated, 3-nitropropionic acid (3-NP) provokes mitochondrial dysfunction and selectively forms striatal lesions similar to those found in Huntington's disease. The current study investigated whether ASK1 is involved in striatal pathology following chronic systemic infusion of 3-NP. The results show that ASK1 acts as a primary mediator of there active oxygen species (ROS) cell death signal cascade in the 3-NP-damaged striatal region by disrupting the positive feedback cycle. In 3-NP-infused striatal lesions, ROS increased ASK1. Superoxide dismutase transgenic (SOD-tg) mice reduced ASK1by scavenging ROS, and reduction of ASK1leads to a reduction in cell death. However, ASK1 down-regulation in 3-NP infusion mice also decreased striatal cell death without scavenging ROS. In contrast decreasing cell death by si-ASK1 treatment along with 3-NP in both SOD tg and wild-type mice (wt), cell death rebounded when ASK1 peptide was added to SOD tg mice. The present study suggests that ROS-inducing ASK1 may be an important step in the pathogenesis of 3-NP infused striatal lesions in murine brains.

hMTH1 expression protects mitochondria from Huntington's disease-like impairment

Huntington disease (HD) is a neurodegenerative disease caused by expansion of CAG repeats in the huntingtin (Htt) gene. The expression of hMTH1, the human hydrolase that degrades oxidized purine nucleoside triphosphates, grants protection in a chemical HD mouse model in which HD-like features are induced by the mitochondrial toxin 3-nitropropionic acid (3-NP). To further examine the relationship between oxidized dNTPs and HD-like neurodegeneration, we studied the effects of hMTH1 expression in a genetic cellular model for HD, such as striatal cells expressing mutant htt (Hdh^Q111). hMTH1 expression protected these cells from 3-NP and H₂O₂-induced killing, by counteracting the mutant htt-dependent increased vulnerability and accumulation of nuclear and mitochondrial DNA 8-hydroxyguanine levels. hMTH1 expression reverted the decreased mitochondrial membrane potential characteristic of Hdh^Q111 cells and delayed the increase in mitochondrial reactive oxygen species associated with 3-NP treatment. Further indications of hMTH1-mediated mitochondrial protection are the partial reversion of 3-NP-induced alterations in mitochondrial morphology and the modulation of DRP1 and MFN1 proteins, which control fusion/fission rates of mitochondria. Finally, in line with the in vitro findings, upon 3-NP in vivo treatment, 8-hydroxyguanine levels in mitochondrial DNA from heart, muscle and brain are significantly lower in transgenic hMTH1-expressing mice than in wild-type animals.

Involvement of the up-regulated FoxO1 expression in follicular granulosa cell apoptosis induced by oxidative stress

Follicular atresia is common in female mammalian ovaries, where most follicles undergo degeneration at any stage of growth and development. Oxidative stress gives rise to triggering granulosa cell apoptosis, which has been suggested as a major cause of follicular atresia. However, the underlying mechanism by which the oxidative stress induces follicular atresia remains unclear. FoxO transcription factors are known as critical mediators in the regulation of oxidative stress and apoptosis. In this study, the involvement of FoxO1 in oxidative stress-induced apoptosis of mouse follicular granulosa cells (MGCs) was investigated in vivo and in vitro. It was observed that increased apoptotic signals correlated with elevated expression of FoxO1 in MGCs when mice were treated with the oxidant. Correspondingly, the expressions of FoxO1 target genes, such as proapoptotic genes and antioxidative genes, were also up-regulated. In primary cultured MGCs, treatment with H(2)O(2) led to FoxO1 nuclear translocation. Further studies with overexpression and knockdown of FoxO1 demonstrated the critical role of FoxO1 in the induction of MGC apoptosis by oxidative stress. Finally, inactivation of FoxO1 by insulin treatment confirmed that FoxO1 induced by oxidative stress played a pivotal role in up-regulating the expression of downstream apoptosis-related genes in MGCs. Our results suggest that up-regulation of FoxO1 by oxidative stress leads to apoptosis of granulosa cells, which eventually results in follicular atresia in mice.

The functional and neuroprotective actions of Neu2000, a dual-acting pharmacological agent, in the treatment of acute spinal cord injury

The goal of the present study was to examine the neuroprotective and functional significance of targeting both N-methyl-D-aspartate (NMDA) receptor-mediated excitotoxicity and oxidative stress using a dual-acting compound, Neu2000, in rat model of moderate spinal cord injury (SCI). An initial set of experiments was conducted in uninjured rats to study the pharmacokinetic profile of Neu2000 following intraperitoneal and intravenous administration. A second experiment measured free radical production in mitochondria isolated from sham or injured spinal cords of animals receiving vehicle or Neu2000 treatment. A third set of animals was divided into three treatment groups consisting of vehicle treatment, a single dose of Neu2000 (50 mg/kg) administered at 10 min following injury, or a repeated treatment paradigm consisting of a single bolus of Neu2000 at 10 min following injury (50 mg/kg) plus a maintenance dose (25 mg/kg) administered every 24 h for an additional 6 days. Animals were tested once a week for a period of 6 weeks for evidence of locomotor recovery in an open field and kinematic analysis of fine motor control using the DigiGait Image Analysis System. At the end of the testing period, spinal cord reconstruction was performed to obtain nonbiased stereological measures of tissue sparing. The results of this study demonstrate that Neu2000 treatment significantly reduced the production of mitochondrial free radicals and improved locomotor outcomes that were associated with a significant increase in the volume of spared spinal cord tissue.

Uncoupling oxidative/energy metabolism with low sub chronic doses of 3-nitropropionic acid or iodoacetate in vivo produces striatal cell damage

A variety of evidence suggests that the failure of cellular metabolism is one of the underlying causes of neurodegenerative diseases. For example, the inhibition of mitochondrial function produces a pattern of cellular pathology in the striatum that resembles that seen in Huntington's disease. However, neurons can also generate ATP through the glycolytic pathway. Recent work has suggested a direct interaction between mutated huntingtin and a key enzyme in the glycolytic pathway, glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Yet little work has been gone into examination of the cellular pathology that results from the inhibition of this alternative energy source. Therefore, the aim of the present study is to characterize the cellular pathology that results in the striatum of mice after treatment with a toxin (iodoacete, IOA) that compromises anaerobic metabolism. This striatal pathology is compared to that produced by a widely studied blocker of mitochondrial function (3-nitropropionic acid, 3-NP). We found that low doses of either toxin resulted in significant pathology in the mouse striatum. Signs of apoptosis were observed in both experimental groups, although apoptosis triggered by IOA treatment was independent from caspase-3 activation. Importantly, each toxin appears to produce cellular damage through distinct mechanisms; only 3-NP generated clear evidence of oxidative stress as well as inhibition of endogenous antioxidants. Understanding the distinct pathological fingerprints of cell loss produced by blockade of oxidative and anaerobic metabolisms may give us insights into neurodegenerative diseases.

Possible neuroprotective effect of Withania somnifera root extract against 3-nitropropionic acid-induced behavioral, biochemical, and mitochondrial dysfunction in an animal model of Huntington's disease

Huntington's disease (HD) is a neurodegenerative disorder that results from the destruction of neurons in the basal ganglia, and oxidative stress has been implicated in its pathogenesis. 3-Nitropropionic acid (3-NP), a potent neurotoxin, has been reported to induce oxidative/nitrosative stress and causes neurobehavioral and biochemical changes that mimic HD in humans. It also inhibits complex II of the mitochondrial electron transport chain, thereby causing cellular energy deficit. In the present work, we evaluated the effects of a well-known antioxidant on behavioral, biochemical, and mitochondrial dysfunction induced by 3-NP. The study was designed to investigate the effects of Withania somnifera root extract against 3-NP-induced gait abnormalities, oxidative stress, and mitochondrial dysfunction in striatum and cortex of rat brain. Intraperitoneal administration of 3-NP (10 mg/kg for 14 days) caused a loss in body weight and a decline in motor function (locomotor activity and impaired rotarod activity). Chronic treatment with W. somnifera root extracts (100 and 200 mg/kg) for a period of 2 weeks dose-dependently improved 3-NP-induced behavioral, biochemical, and enzymatic changes (P < .05). Biochemical analysis revealed that systemic 3-NP administration significantly increased lipid peroxidation and nitrite and lactate dehydrogenase enzyme levels, depleted antioxidant enzyme (superoxide dismutase and catalase) levels, and blocked ATP synthesis by inhibiting the mitochondrial complex activity in the different regions (striatum and cortex) of the brain. Chronic administration of W. somnifera root extract (100 and 200 mg/kg) dose-dependently restored biochemical alterations induced by chronic 3-NP treatment (P < .05). These findings suggest that neuroprotective actions of W. somnifera are mediated via its antioxidant activity. However, further studies are required to elucidate the molecular mechanisms involved in order to support the clinical use of the plant extract as a therapeutic agent for the treatment of HD.

Peroxiredoxin II preserves cognitive function against age-linked hippocampal oxidative damage

Reactive oxygen species (ROS), routinely produced in biological reactions, contribute to both normal aging and age-related decline in cognitive function. However, little is known regarding the involvement of specific antioxidants in the underlying mechanism(s). Here, we examined if peroxiredoxin II (Prx II) scavenges intracellular ROS that cause age-dependent mitochondrial decay in hippocampal CA1 pyramidal neurons and subsequent impairment of learning and memory. Age-dependent mitochondrial ROS generation and long-term potentiation (LTP) decline were more prominent in hippocampal neurons in Prx II(-/-) than in wild-type mice. Additionally, Prx II(-/-) mice failed to activate synaptic plasticity-related cellular signaling pathways involving CREB, CaMKII, and ERK, or to maintain functional integrity of their mitochondria. Dietary vitamin E alleviated Prx II deficiency-related deficits, including mitochondrial decay and CREB signaling, resulting in restoration of the abrupt cognitive decline in aged Prx II(-/-) mice. These results suggest that Prx II help maintain hippocampal synaptic plasticity against age-related oxidative damage.

Mitochondrial DNA damage is a hallmark of chemically induced and the R6/2 transgenic model of Huntington's disease

Many forms of neurodegeneration are associated with oxidative stress and mitochondrial dysfunction. Mitochondria are prominent targets of oxidative damage, however, it is not clear whether mitochondrial DNA (mtDNA) damage and/or its lack of repair are primary events in the delayed onset observed in Huntington's disease (HD). We hypothesize that an age-dependent increase in mtDNA damage contributes to mitochondrial dysfunction in HD. Two HD mouse models were studied, the 3-nitropropionic acid (3-NPA) chemically induced model and the HD transgenic mice of the R6/2 strain containing 115-150 CAG repeats in the huntingtin gene. The mitochondrial toxin 3-NPA inhibits complex II of the electron transport system and causes neurodegeneration that resembles HD in the striatum of human and experimental animals. We measured nuclear and mtDNA damage by quantitative PCR (QPCR) in striatum of 5- and 24-month-old untreated and 3-NPA treated C57BL/6 mice. Aging caused an increase in damage in both nuclear and mitochondrial genomes. 3-NPA induced 4-6 more damage in mtDNA than nuclear DNA in 5-month-old mice, and this damage was repaired by 48h in the mtDNA. In 24-month-old mice 3NPA caused equal amounts of nuclear and mitochondrial damage and this damage persistent in both genomes for 48h. QPCR analysis showed a progressive increase in the levels of mtDNA damage in the striatum and cerebral cortex of 7-12-week-old R6/2 mice. Striatum exhibited eight-fold more damage to the mtDNA compared with a nuclear gene. These data suggest that mtDNA damage is an early biomarker for HD-associated neurodegeneration and supports the hypothesis that mtDNA lesions may contribute to the pathogenesis observed in HD.

Mitochondrial dysfunction: the first domino in brain aging and Alzheimer's disease?

With the increasing average life span of humans and with decreasing cognitive function in elderly individuals, age-related cognitive disorders including dementia have become a major health problem in society. Aging-related mitochondrial dysfunction underlies many common neurodegenerative disorders diseases, including Alzheimer's disease (AD). AD is characterized by two major histopathological hallmarks, initially intracellular and with the progression of the disease extracellular accumulation of oligomeric and fibrillar beta-amyloid (Abeta) peptides and intracellular neurofibrillary tangles (NFT) composed of hyperphosphorylated tau protein. In this review, the authors focus on the latest findings in AD animal models indicating that these histopathological alterations induce deficits in the function of the complexes of the respiratory chain and therefore consecutively result in mitochondrial dysfunction. This parameter is intrinsically tied to oxidative stress. Both are early events in aging and especially in the pathogenesis of aging-related severe neurodegeneration. Ginkgo biloba extract seems to be of therapeutic benefit in the treatment of mild to moderate dementia of different etiology, although the data are quite heterogeneous. Herein, the authors suggest that mitochondrial protection and subsequent reduction of oxidative stress are important components of the neuroprotective activity of Ginkgo biloba extract.

Mitochondrial UCP4 mediates an adaptive shift in energy metabolism and increases the resistance of neurons to metabolic and oxidative stress

The high-metabolic demand of neurons and their reliance on glucose as an energy source places them at risk for dysfunction and death under conditions of metabolic and oxidative stress. Uncoupling proteins (UCPs) are mitochondrial inner membrane proteins implicated in the regulation of mitochondrial membrane potential (Deltapsim) and cellular energy metabolism. The authors cloned UCP4 cDNA from mouse and rat brain, and demonstrate that UCP4 mRNA is expressed abundantly in brain and at particularly high levels in populations of neurons believed to have high-energy requirements. Neural cells with increased levels of UCP4 exhibit decreased Deltapsim, reduced reactive oxygen species (ROS) production and decreased mitochondrial calcium accumulation. UCP4 expressing cells also exhibited changes of oxygen-consumption rate, GDP sensitivity, and response of Deltapsim to oligomycin that were consistent with mitochondrial uncoupling. UCP4 modulates neuronal energy metabolism by increasing glucose uptake and shifting the mode of ATP production from mitochondrial respiration to glycolysis, thereby maintaining cellular ATP levels. The UCP4-mediated shift in energy metabolism reduces ROS production and increases the resistance of neurons to oxidative and mitochondrial stress. Knockdown of UCP4 expression by RNA interference in primary hippocampal neurons results in mitochondrial calcium overload and cell death. UCP4-mRNA expression is increased in neurons exposed to cold temperatures and in brain cells of rats maintained on caloric restriction, suggesting a role for UCP4 in the previously reported antiageing and neuroprotective effects of caloric restriction. By shifting energy metabolism to reduce ROS production and cellular reliance on mitochondrial respiration, UCP4 can protect neurons against oxidative stress and calcium overload.

Oxidative damage in Huntington's disease pathogenesis

Huntington's disease (HD) is a devastating neurodegenerative disorder characterized by the progressive development of involuntary choreiform movements, cognitive impairment, neuropsychiatric symptoms, and premature death. These phenotypes reflect neuronal dysfunction and ultimately death in selected brain regions, the striatum and cerebral cortex being principal targets. The genetic mutation responsible for the HD phenotype is known, and its protein product, mutant huntingtin (mhtt), identified. HD is one of several "triplet repeat" diseases, in which abnormal expansions in trinucleotide repeat domains lead to elongated polyglutamine stretches in the affected gene's protein product. Mutant htt-mediated toxicity in the brain disrupts a number of vital cellular processes in the course of disease progression, including energy metabolism, gene transcription, clathrin-dependent endocytosis, intraneuronal trafficking, and postsynaptic signaling, but the crucial initiation mechanism induced by mhtt is still unclear. A large body of evidence, however, supports an early and critical involvement of defects in mitochondrial function and CNS energy metabolism in the disease trigger. Thus, downstream death-effector mechanisms, including excitotoxicity, apoptosis, and oxidative damage, have been implicated in the mechanism of selective neuronal damage in HD. Here we review the current evidence supporting a role for oxidative damage in the etiology of neuronal damage and degeneration in HD.

Oral uridine pro-drug PN401 is neuroprotective in the R6/2 and N171-82Q mouse models of Huntington's disease

Previously, uridine pro-drug 2',3',5'-tri-O-acetyluridine (PN401) was shown to be protective in the mitochondrial complex II inhibitor 3-nitropropionic acid model of Huntington's disease (HD). In this study, PN401 increased survival and improved motor function on the rotarod in both R6/2 and N171-82Q polyglutamine repeat mouse models of HD. PN401 significantly decreased neurodegeneration in both the piriform cortex and striatum although PN401 decreased huntingtin protein aggregates only in the striatum. Cortical and striatal brain-derived neurotrophic factor (BDNF) protein levels were reduced in the +/- compared to the -/- N171-82Q mice and PN401 treatment significantly increased cortical BDNF in both +/- and -/- mice, but PN401 did not affect striatal BDNF. These results suggest that PN401 may have beneficial effects in the treatment of neurodegenerative diseases such as HD.

Effect of resveratrol on 3-nitropropionic acid-induced biochemical and behavioural changes: possible neuroprotective mechanisms

Huntington's disease is a progressive, degenerative disease characterized by abnormal body movements called chorea, and a reduction of various mental abilities. 3-Nitropropionic acid, an inhibitor of complex II of the electron transport chain, causes Huntington's disease-like symptoms in rodents. Recently, it has been reported that oxidative stress, which is one of the pathological hallmarks of various neurodegenerative disorders, also plays an important role in the pathogenesis of Huntington's disease. The present study was designed to investigate effects of resveratrol, an antioxidant with cyclooxygenase I inhibitory activity, in the 3-nitropropionic acid-induced model of Huntington's disease. Intraperitoneal administration of 3-nitropropionic acid (20 mg/kg for 4 days) caused significant loss of body weight, a decline in motor function (locomotor activity, movement pattern and vacuous chewing movements) and poor retention of memory. Repeated treatment with resveratrol (5 and 10 mg/kg, orally), once daily for a period of 8 days beginning 4 days prior to 3-nitropropionic acid administration, significantly improved the 3-nitropropionic acid-induced motor and cognitive impairment. Biochemical analysis revealed that systemic 3-nitropropionic acid administration significantly increased lipid peroxidation, nitrite levels, and depleted reduced glutathione levels, and decreased succinate dehydrogenase activity in the brains of rats. The results of the present study indicate that resveratrol (5 and 10 mg/kg, orally) significantly reversed 3-nitropropionic acid-induced motor and cognitive impairment, and that the beneficial effects of resveratrol might be attributed to its antioxidant activity.

Localization of superoxide anion production to mitochondrial electron transport chain in 3-NPA-treated cells

3-Nitropropionic acid (3-NPA), an inhibitor of succinate dehydrogenase (SDH) at complex II of the mitochondrial electron transport chain induces cellular energy deficit and oxidative stress-related neurotoxicity. In the present study, we identified the site of reactive oxygen species production in mitochondria. 3-NPA increased O2- generation in mitochondria respiring on the complex I substrates pyruvate+malate, an effect fully inhibited by rotenone. Antimycin A increased O2- production in the presence of complex I and/or II substrates. Addition of 3-NPA markedly increased antimycin A-induced O2- production by mitochondria incubated with complex I substrates, but 3-NPA inhibited O2- formation driven with the complex II substrate succinate. At 0.6 microM, myxothiazol inhibits complex III, but only partially decreases complex I activity, and allowed 3-NPA-induced O2- formation; however, at 40 microM myxothiazol (which completely inhibits both complexes I and III) eliminated O2- production from mitochondria respiring via complex I substrates. These results indicate that in the presence of 3-NPA, mitochondria generate O2- from a site between the ubiquinol pool and the 3-NPA block in the respiratory complex II.

Ageing and neuronal vulnerability

Everyone ages, but only some will develop a neurodegenerative disorder in the process. Disease might occur when cells fail to respond adaptively to age-related increases in oxidative, metabolic and ionic stress, thereby resulting in the accumulation of damaged proteins, DNA and membranes. Determinants of neuronal vulnerability might include cell size and location, metabolism of disease-specific proteins and a repertoire of signal transduction pathways and stress resistance mechanisms. Emerging evidence on protein interaction networks that monitor and respond to the normal ageing process suggests that successful neural ageing is possible for most people, but also cautions that cures for neurodegenerative disorders are unlikely in the near future.

Protective effects of S-nitrosoglutathione against neurotoxicity of 3-nitropropionic acid in rat

Mitochondrial dysfunction and oxidative stress are often linked to various neurodegenerative disorders including ischemic stroke and Huntington's disease (HD). S-Nitrosoglutathione (GSNO) is an endogenous nitric oxide carrier recently identified as a potent antioxidant capable of neutralizing oxidative stress. In the present study, we explore the neuroprotective effects of GSNO against metabolic insults induced by 3-nitropropionic acid (3-NP), a mitochondrial complex II inhibitor commonly used as a pharmacological model for HD, in primary culture of fetal rat cortical and striatal neurons. Application of GSNO (1-5 microM) substantially reduced neuronal loss caused by 3-NP (1-5 mM) exposure based on MTT reduction, lactate dehydrogenase (LDH) release, and Hoechst staining assays. The protective effect of GSNO appeared to be more potent than N-acetyl-l-cysteine (NAC), a glutathione precursor, at the same concentrations. These results suggest that manipulation of GSNO metabolism may exert protective effects against mitochondrial dysfunction often observed in neurodegenerative disorders.

Experimental basis for the putative role of GluR6/kainate glutamate receptor subunit in Huntington's disease natural history

Age of onset of Huntington's disease (HD) statistically correlates with the length of expanded CAG repeats in the IT15 gene. However, other factors such as polymorphism in the 3' untranslated region of the GluR6 kainate receptor gene subunit may contribute to variability in the age at onset. To investigate this issue, we studied the motor disorder and related striatal damage induced by 3-nitropropionic acid (3-NP) subacute administration in GluR6 knockout mice (GluR6(-/-)) as compared to wild-type mice. In two different age groups (6 months and 1 year), we observed that GluR6(-/-) mice did not display more motor impairment nor more striatal histopathological damage than GluR6(+/+) mice, although 1-year-old GluR6(-/-) mice displayed reduced activity parameters either at baseline or after 3-NP administration compared to GluR6(+/+). In both age groups, GluR6(-/-) mice died earlier and displayed earlier motor symptoms during 3-NP-induced metabolic compromise, suggesting that GluR6-containing kainate receptors may be implicated during neurodegeneration, such as in HD, rather than in the final outcome.

Oral uridine pro-drug PN401 decreases neurodegeneration, behavioral impairment, weight loss and mortality in the 3-nitropropionic acid mitochondrial toxin model of Huntington's disease

Huntington's disease (HD) is associated with decreased activity of mitochondrial succinate dehydrogenase (complex II). De novo biosynthesis of uridine nucleotides is directly coupled to the respiratory chain. Cells with impaired mitochondrial function become uridine auxotrophs and can be maintained with high micromolar concentration of uridine and pyruvate. The therapeutic role of pyrimidines and possible changes in uridine content has not been assessed in neurological diseases involving mitochondrial dysfunction in vivo. Oral administration of PN401 delivers much higher levels of uridine to the circulation than oral administration of uridine itself. Administration of complex II inhibitor 3-nitropropionic acid (3NP) induced neuronal damage in the striatum, substantia nigra and/or thalamus in 80% of the mice and led to 38% mortality. Treatment with PN401 almost completely prevented the neuronal damage due to 3NP and completely prevented mortality. In two subsequent experiments, 3NP-induced weight loss, mortality and behavioral impairment in rotarod performance and spontaneous motor activity were attenuated by treatment with oral PN401. 3NP did not reduce forebrain total uridine nucleotides (TUN), though higher doses of PN401 associated with optimal neuroprotection did elevate TUN to supranormal levels. Thus, oral PN401 treatment has neuroprotective effects in a HD model of mitochondrial dysfunction and the mechanism is more complex than correction of a pyrimidine deficit.

Magnetic resonance imaging and spectroscopy in assessing 3-nitropropionic acid-induced brain lesions: an animal model of Huntington’s disease

Huntington's disease (HD) is an inherited neurodegenerative disease, in which there is progressive motor and cognitive deterioration, and for which the pathogenesis of neuronal death remains controversial. Mitochondrial toxins like 3-nitropropionic acid (3-NP) and malonate, functioning as the inhibitors of the complex II of mitochondrial respiratory chain, have been found to effectively induce specific behavioral changes and selective striatal lesions in rats and non-human primates mimicking those in HD. Furthermore, several kinds of transgenic mouse models of HD have been recently developed, and used in the development and assessment of novel treatments for HD. In the past, most studies evaluating the animal models for HD were based on histological changes or in vitro neuronal cultures. With the emergence of advanced magnetic resonance technologies, non-invasive magnetic resonance imaging (MRI) and spectroscopy provide more detail of cerebral alterations, including the changes of cerebral structure, function and metabolites. These studies support the hypothesis that mitochondrial dysfunction with increased excitation of N-methyl-D-aspartate (NMDA) receptors can replicate the neurobehavioral changes, selective brain injury and neurochemical alterations in HD. The present review focuses on our work as well as that of others regarding 3-NP-induced neurotoxicity and other animal models of HD. Using both conventional and advanced MRI and spectroscopy, we summarize the pathogenesis and possible therapeutic strategies in chemical and transgenic models of HD. The results show magnetic resonance techniques to be powerful techniques in the evaluation of pathogenesis and therapeutic intervention for both chemical and transgenic models of HD.

Neurodegeneration in striatum induced by the mitochondrial toxin 3-nitropropionic acid: role of matrix metalloproteinase-9 in early blood-brain barrier disruption?

Blood-brain barrier (BBB) dysfunction is a potential mechanism involved in progressive striatal damage induced by the mitochondrial excitotoxin, 3-nitropropionic acid (3-NP). After activation by proteases and free radicals, matrix metalloproteinases (MMPs), particularly MMP-9 and -2, can digest the endothelial basal lamina leading to BBB opening. Using CD-1 mice, we show that MMP-9 expression by zymography is increased in the injured striatum compared with the contralateral striatum 2 hr after 3-NP injection [133.50 +/- 57.17 vs 50.25 +/- 13.56; mean +/- SD of optical densities in arbitrary units (A.U.); p < 0.005] and remains elevated until 24 hr (179.33 +/- 78.24 A.U.). After 4 hr, MMP-9 expression and activation are accompanied by an increase in BBB permeability. MMP inhibition attenuates BBB disruption, swelling, and lesion volume compared with vehicle-treated controls. There is a clear spatial relationship between MMP-9 expression and oxidized hydroethidine, indicating reactive oxygen species (ROS) production. Furthermore, transgenic mice that overexpress copper/zinc-superoxide dismutase (SOD1) show decreased lesion size and edema along with decreased immunoreactivity for MMP-9, compared with wild-type littermates (lesion: 38.8 +/- 15.1 and 53.3 +/- 10.3, respectively, p < or = 0.05; edema: 21.8 +/- 11.2 and 35.28 +/- 11, respectively, p < or = 0.05; MMP-9-positive cells: 352 +/- 57 and 510 +/- 45, respectively, p < or = 0.005), whereas knock-out mice deficient in SOD1 display significantly greater swelling (48.65 +/- 17; p < or = 0.05). We conclude that early expression and activation of MMP-9 by ROS may be involved in early BBB disruption and progressive striatal damage after 3-NP treatment.

Treatment with dihydroethidium reduces infarct size after transient focal cerebral ischemia in mice

A transient focal ischemia model with C57Bl/6 mice was used to investigate whether dihydroethidium is neuroprotective. Different doses (25, 50, 100 mg/kg body weight) were used for pretreatment and the lowest effective dose was used for delayed treatment 1 and 2 h after reperfusion. Our results demonstrate that all the doses used for treatment reduced infarct volume. We conclude that dihydroethidium is neuroprotective by reducing superoxide in mice after stroke.

Apoptosis in Huntington's disease

Huntington's disease (HD) is an autosomal dominant, fatal disorder. Patients display increasing motor, psychiatric and cognitive impairment and at autopsy, late-stage patient brains show extensive striatal (caudate and putamen), pallidal and cortical atrophy. The initial and primary target of degeneration in HD is the striatal medium spiny GABAergic neuron, and by end stages of the disease up to 95% of these neurons are lost [J. Neuropathol. Exp. Neurol. 57 (1998) 369]. The disease is caused by an elongation of a polyglutamine tract in the N-terminal of the huntingtin gene, but it is not known how this mutation leads to such extensive, but selective, cell death [Cell 72 (1993) 971]. There is substantial evidence from in vitro studies that connects apoptotic pathways and apoptosis with the mutant protein, and theories linking apoptosis to neuronal death in HD have existed for several years. Despite this, evidence of apoptotic neuronal death in HD is scarce. It may be that the processes involved in apoptosis, rather than apoptosis per se, are more important for HD pathogenesis. Upregulation of the proapoptotic proteins could lead to cleavage of huntingtin and as recent data has shown, the consequent toxic fragment may itself elicit toxic effects on the cell by disrupting transcription. In addition, the increased levels of proapoptotic proteins could contribute to slowly developing cell death in HD, selective for the striatal medium spiny GABAergic neurons and later spreading to other areas. Here we review the evidence supporting these mechanisms of pathogenesis in HD.

Subacute systemic 3-nitropropionic acid intoxication induces a distinct motor disorder in adult C57Bl/6 mice: behavioural and histopathological characterisation

Data on motor behavioural disorders induced by systemic 3-nitropropionic acid, an irreversible inhibitor of mitochondrial succinate dehydrogenase and their histopathological correlates in mice, are sparse. We thus further characterised the subacute 3-nitropropionic-acid-induced motor disorder and its time course in C57Bl/6 mice using standard behavioural tests, histopathological correlates and in vivo magnetic resonance imaging. Firstly, we studied two intoxication paradigms (340 and 560 mg 3-nitropropionic acid/kg, 7 days) compared to controls. The low-dose regimen induced only slight motor changes (reduced hindlimb stride length and rearing). The high-dose regimen induced significant (P<0.05) behavioural and sensorimotor integration deficits (pole test, rotarod, stride length, open-field spontaneous activity) but with 37.5% lethality at week one. The clinical motor disorder consisted of hindlimb clasping and dystonia, truncal dystonia, bradykinesia and impaired postural control. Histopathologically, there were discrete lesions of the dorsolateral striatum in 62.5% of mice together with a 32% reduction (P<0.0001) of the striatal volume, reduced caldbindin-D28K immunoreactivity in the lateral striatum, and met-enkephalin and substance P in the striatal output pathways. There was also a significant (P<0.05) 30-40% dopaminergic cell loss within the substantia nigra pars compacta. Secondly, we validated a semi-quantitative behavioural scale to describe the time course of the motor deficits and to predict the occurrence of striatal damage. We sought to determine whether it could also be disclosed in vivo by magnetic resonance imaging. The scale correlated with the striatal volume reduction (r(2)=0.57) and striatal cell loss (r(2)=0.87) but not with the loss of striatal dopaminergic terminals (dopamine transporter binding). Increased T2-signal intensity within the striatal lesion correlated with the cell loss (r(2)=0.66). We conclude that systemic administration of 3-nitropropionic acid in C57Bl/6 mice induces a distinct motor disorder and dose-dependent striatonigral damage, which are potentially useful to model human diseases of the basal ganglia.

Analysis of mitochondrial free radical generation in animal models of neuronal disease

Mitochondria, the power plant of all eukaryotic cells, produce cellular energy in the form of ATP via electron transport and oxidative phosphorylation. However, the mitochondria leak electrons that can act as major sources of oxidative stress, and their dysfunction, have been proposed as causative events underlying neurodegeneration in stroke and neurodegenerative diseases. We examined whether MitoTracker Red CM-H(2)XRos, a rosamine derivative used to detect mitochondrial free radicals in vitro, would be applied to analyze the mitochondrial free radicals in various models of neurological diseases in vivo. The injections of MitoTracker Red CM-H(2)XRos revealed generation of mitochondrial free radicals primarily in vulnerable neurons following focal cerebral ischemia as well as administration of Fe(2+) or 3-nitropropionic acid. MitoTracker Red CM-H(2)XRos was retained after fixation, compatible with immunocytochemistry or nuclear staining, and can be applied to study roles of mitochondrial free radicals in the process of neurodegeneration in vivo.

3-Nitropropionic acid neurotoxicity in hippocampal slice cultures: developmental and regional vulnerability and dependency on glucose

We investigated whether neurotoxic effects of the mitochondrial toxin 3-nitropropionic acid (3-NP) in hippocampal slice cultures are dependent on glucose levels in the culture medium and whether such effects occur via apoptosis or necrosis. In addition, 3-NP toxicity was investigated at two developmental stages of the cultures, prepared from rat brain at postnatal day 5-7 and grown in Neurobasal medium for 1 or 3 weeks. Cultures were exposed to 3-NP in the presence of high (25 mM), normal (5 mM), or low (3 mM) glucose for 48 h, followed by 48 h incubation in medium without 3-NP. Cellular propidium iodide (PI) uptake and lactate dehydrogenase (LDH) efflux into the medium revealed time- and dose-dependent cell death by 3-NP, with EC(50) values of about 60 microM in high or normal glucose. Regional vulnerability, as assessed by PI uptake and MAP2 immunostaining, in 3-week-old cultures was as follows: CA1 > CA3 > fascia dentata. In low glucose much lower concentrations of 3-NP (25 microM) triggered neurotoxicity. One-week-old cultures were less susceptible to 3-NP toxicity than 3-week-old cultures, but the dentate granule cells were relatively more affected in the immature cultures. We found no evidence for apoptotic cell death by 3-NP in 3-week-old cultures, but in 1-week-old cultures the putative apoptotic marker c-JUN/AP1 and nuclear fragmentation (Hoechst) were significantly increased in the dentate granule cells.

Involvement of superoxide in excitotoxicity and DNA fragmentation in striatal vulnerability in mice after treatment with the mitochondrial toxin, 3-nitropropionic acid

Oxidative stress and excitotoxicity have been implicated in selective striatal vulnerability caused by the mitochondrial toxin, 3-nitropropionic acid (3-NP), which may simulate Huntington's disease in animals and humans. The detailed mechanism of the role of superoxide in striatal vulnerability induced by 3-NP is still unknown. The authors investigated oxidative cellular injury and DNA fragmentation after systemic 3-NP injection in wild-type (Wt) mice and mutant mice with a deficiency in manganese superoxide dismutase (MnSOD; Sod2 -/+). Furthermore, they investigated the effects of decortication after 3-NP treatment in Sod2 -/+ mice, and copper/zinc SOD (CuZnSOD) treatment in recently developed Sod2 -/+ mice that overexpress CuZnSOD (SOD1 +/- / Sod2 -/+ mice). Oxidized hydroethidine, 8-hydroxyguanosine immunoreactivity, and nitrotyrosine immunoreactivity were increased in the Sod2 -/+ mice compared with the Wt mice after 3-NP treatment (P < 0.001). Decortication completely abolished oxidative striatal damage after 3-NP treatment in the Sod2 -/+ mice. Increased CuZnSOD attenuated DNA fragmentation and striatal lesion volume after 3-NP treatment in the Sod2 -/+ mice (P < 0.001). These data suggest that production of superoxide may be a critical step to excitotoxicity and subsequent DNA fragmentation in selective striatal vulnerability after 3-NP treatment.

Dopamine transporter knock-out mice are hypersensitive to 3-nitropropionic acid-induced striatal damage

Evidence suggests that dopamine is involved in the modulation of striatal excitotoxic processes. To further investigate this issue, we studied the effects of systemic 'low-dose' (total dose, 340 mg/kg in 7 days) 3-nitropropionic acid (3-NP) intoxication in dopamine transporter knock-out mice (DAT-/-) compared to wildtype (DAT+/+) mice. Systemic 'low-dose' 3-NP induced a significant impairment in a rotarod task only in DAT-/- mice. Histopathology also demonstrated a significant reduction of the striatal volume (-7%, P < 0.05), neuronal density (-12.5%, P < 0.001) and absolute number estimates of striatal neurons (-11.5%, P < 0.001) in DAT-/- compared to DAT+/+ mice, with increased glial activation, independent of the degree of succinate dehydrogenase inhibition. These findings strengthen the hypothesis for dopamine modulation of excitotoxicity within the nigrostriatal system.

Manganese superoxide dismutase deficiency exacerbates cerebral infarction after focal cerebral ischemia/reperfusion in mice: implications for the production and role of superoxide radicals

BACKGROUND AND PURPOSE

Superoxide anion radicals (O2*-) are implicated in ischemia/reperfusion injury, although a direct relationship has not been elucidated. Recently, a specific method of hydroethidine (HEt) oxidation by O2*- was developed to detect O2*- production in a variety of experimental brain injury models. To clarify the role of O2*- in the mechanism of ischemia/reperfusion, we investigated O2*- production after ischemia/reperfusion and ischemia/reperfusion injury in mutant mice deficient in mitochondrial manganese superoxide dismutase (MnSOD) and in wild-type littermates.

METHODS

Ischemia/reperfusion was performed for 60 minutes using intraluminal suture blockade of the middle cerebral artery in the mutant or wild-type mice. We evaluated fluorescent kinetics of HEt or ethidium, the oxidized form of HEt, in brains after an intravenous injection of HEt, followed by measurement of cellular O2*- production using specific HEt oxidation by O2*- before and after ischemia/reperfusion. Furthermore, we compared O2*- production and subsequent infarct volume in the mice using triphenyltetrazolium chloride after ischemia/reperfusion.

RESULTS

HEt oxidation to ethidium is primarily a result of mitochondrially produced O2*- under physiological conditions. Cerebral ischemia/reperfusion produced O2*- prominently in neurons shortly after reperfusion, followed by a delayed increase in endothelial cells. A deficiency in MnSOD in mutant mice increased mitochondrial O2*- production and exacerbated cerebral infarction, worsening neurological deficits after ischemia/reperfusion.

CONCLUSION

These results suggest that mitochondrial O2*- production may be a critical step underlying the mechanism of ischemia/reperfusion injury and that MnSOD may protect against ongoing oxidative cell death after ischemia/reperfusion.