Induction of oxidative stress by chronic and acute glutaric acid administration to rats

Metabolic Regulation of Copper Toxicity during Marine Mussel Embryogenesis

The development of new tools for assessing the health of cultured shellfish larvae is crucial for aquaculture industries to develop and refine hatchery methodologies. We established a large-volume ecotoxicology/health stressor trial, exposing mussel (Perna canaliculus) embryos to copper in the presence of ethylenediaminetetraacetic acid (EDTA). GC/MS-based metabolomics was applied to identify potential biomarkers for monitoring embryonic/larval health and to characterise mechanisms of metal toxicity. Cellular viability, developmental abnormalities, larval behaviour, mortality, and a targeted analysis of proteins involved in the regulation of reactive oxygen species were simultaneously evaluated to provide a complementary framework for interpretative purposes and authenticate the metabolomics data. Trace metal analysis and speciation modelling verified EDTA as an effective copper chelator. Toxicity thresholds for P. canaliculus were low, with 10% developmental abnormalities in D-stage larvae being recorded upon exposure to 1.10 μg·L-1 bioavailable copper for 66 h. Sublethal levels of bioavailable copper (0.04 and 1.10 μg·L-1) caused coordinated fluctuations in metabolite profiles, which were dependent on development stage, treatment level, and exposure duration. Larvae appeared to successfully employ various mechanisms involving the biosynthesis of antioxidants and a restructuring of energy-related metabolism to alleviate the toxic effects of copper on cells and developing tissues. These results suggest that regulation of trace metal-induced toxicity is tightly linked with metabolism during the early ontogenic development of marine mussels. Lethal-level bioavailable copper (50.3 μg·L-1) caused severe metabolic dysregulation after 3 h of exposure, which worsened with time, substantially delayed embryonic development, induced critical oxidative damage, initiated the apoptotic pathway, and resulted in cell/organism death shortly after 18 h of exposure. Metabolite profiling is a useful approach to (1) assess the health status of marine invertebrate embryos and larvae, (2) detect early warning biomarkers for trace metal contamination, and (3) identify novel regulatory mechanisms of copper-induced toxicity.

Identification of Biomarkers for Methamphetamine Exposure Time Prediction in Mice Using Metabolomics and Machine Learning Approaches

Methamphetamine (METH) abuse has become a global public health and safety problem. More information is needed to identify the time of drug abuse. In this study, methamphetamine was administered to male C57BL/6J mice with increasing doses from 5 to 30 mg kg^-1 (once a day, i.p.) for 20 days. Serum and urine samples were collected for metabolomics studies using gas chromatography-mass spectrometry (GC-MS). Six machine learning models were used to infer the time of drug abuse and the best model was selected to predict administration time preliminarily. The metabolic changes caused by methamphetamine were explored. As results, the metabolic patterns of methamphetamine exposure mice were quite different from the control group and changed over time. Specifically, serum metabolomics showed enhanced amino acid metabolism and increased fatty acid consumption, while urine metabolomics showed slowed metabolism of the tricarboxylic acid (TCA) cycle, increased organic acid excretion, and abnormal purine metabolism. Phenylalanine in serum and glutamine in urine increased, while palmitic acid, 5-HT, and monopalmitin in serum and gamma-aminobutyric acid in urine decreased significantly. Among the six machine learning models, the random forest model was the best to predict the exposure time (serum: MAE = 1.482, RMSE = 1.69, R squared = 0.981; urine: MAE = 2.369, RMSE = 1.926, R squared = 0.946). The potential biomarker set containing four metabolites in the serum (palmitic acid, 5-hydroxytryptamine, monopalmitin, and phenylalanine) facilitated the identification of methamphetamine exposure. The random forest model helped predict the methamphetamine exposure time based on these potential biomarkers.

Disturbance of Mitochondrial Dynamics, Endoplasmic Reticulum-Mitochondria Crosstalk, Redox Homeostasis, and Inflammatory Response in the Brain of Glutaryl-CoA Dehydrogenase-Deficient Mice: Neuroprotective Effects of Bezafibrate

Patients with glutaric aciduria type 1 (GA1), a neurometabolic disorder caused by deficiency of glutaryl-CoA dehydrogenase (GCDH) activity, commonly manifest acute encephalopathy associated with severe striatum degeneration and progressive cortical and striatal injury whose pathogenesis is still poorly known. We evaluated redox homeostasis, inflammatory response, mitochondrial biogenesis and dynamics, endoplasmic reticulum (ER)-mitochondria crosstalk, and ER stress in the brain of GCDH-deficient (Gcdh^-/-) and wild-type (Gcdh^+/+) mice fed a high Lys chow, which better mimics the human neuropathology mainly characterized by striatal lesions. Increased lipid peroxidation and altered antioxidant defenses, including decreased concentrations of reduced glutathione and increased activities of superoxide dismutase, catalase, and glutathione transferase, were observed in the striatum and cerebral cortex of Gcdh^-/- mice. Augmented Iba-1 staining was also found in the dorsal striatum and neocortex, whereas the nuclear content of NF-κB was increased, and the cytosolic content of IκBα decreased in the striatum of the mutant animals, indicating a pro-inflammatory response. Noteworthy, in vivo treatment with the pan-PPAR agonist bezafibrate normalized these alterations. It was also observed that the ER-mitochondria crosstalk proteins VDAC1 and IP3R were reduced, whereas the ER stress protein DDIT3 was augmented in Gcdh^-/- striatum, signaling disturbances of these processes. Finally, DRP1 content was elevated in the striatum of Gcdh^-/- mice, indicating activated mitochondrial fission. We presume that some of these novel pathomechanisms may be involved in GA1 neuropathology and that bezafibrate should be tested as a potential adjuvant therapy for GA1.

Disruption of mitochondrial functions and oxidative stress contribute to neurologic dysfunction in organic acidurias

Organic acidurias (OADs) are inherited disorders of amino acid metabolism biochemically characterized by accumulation of short-chain carboxylic acids in tissues and biological fluids of the affected patients and clinically by predominant neurological manifestations. Some of these disorders are amenable to treatment, which significantly decreases mortality and morbidity, but it is still ineffective to prevent long-term neurologic and systemic complications. Although pathogenesis of OADs is still poorly established, recent human and animal data, such as lactic acidosis, mitochondrial morphological alterations, decreased activities of respiratory chain complexes and altered parameters of oxidative stress, found in tissues from patients and from genetic mice models with these diseases indicate that disruption of critical mitochondrial functions and oxidative stress play an important role in their pathophysiology. Furthermore, organic acids that accumulate in the most prevalent OADs were shown to compromise bioenergetics, by decreasing ATP synthesis, mitochondrial membrane potential, reducing equivalent content and calcium retention capacity, besides inducing mitochondrial swelling, reactive oxygen and nitrogen species generation and apoptosis. It is therefore presumed that secondary mitochondrial dysfunction and oxidative stress caused by major metabolites accumulating in OADs contribute to tissue damage in these pathologies.

Lipopolysaccharide-Elicited Systemic Inflammation Induces Selective Vulnerability of Cerebral Cortex and Striatum of Developing Glutaryl-CoA Dehydrogenase Deficient (Gcdh-/-) Mice to Oxidative Stress

We investigated redox homeostasis in cerebral and peripheral tissues of wild type (WT) and glutaryl-CoA dehydrogenase knockout mice (Gcdh^-/-) submitted to inflammation induced by lipopolysaccharide (LPS) since patients with glutaric aciduria type I (GA I) manifest acute encephalopathy during catabolic events triggered by inflammation. WT and Gcdh^-/- mice fed a low (0.9%) or high (4.7%) Lys chow were euthanized 4 h after LPS intraperitoneal injection. Cerebral cortex of Lys-restricted Gcdh^-/- animals presented no alterations of redox homeostasis, whereas those fed a high Lys chow showed increased malondialdehyde (MDA) levels and superoxide dismutase (SOD) activity, compared to WT mice. Furthermore, Gcdh^-/- mice receiving low Lys and injected with LPS presented elevated MDA levels and decreased reduced glutathione (GSH) concentrations, glutathione peroxidase (GPx), and glutathione reductase (GR) activities in cerebral cortex. LPS administration also decreased GSH values, as well as GPx and GR activities in cerebral cortex of Gcdh^-/- mice receiving Lys overload. Further experiments performed in WT and Gcdh^-/- mice injected with LPS and receiving either a low or high Lys chow revealed increased MDA levels and decreased GSH concentrations in cerebral cortex and striatum, but not in hippocampus, liver and heart of Gcdh^-/- mice, suggesting a selective vulnerability of these cerebral structures to oxidative stress during an inflammatory process. LPS administration also increased S100B and NF-κF protein levels in brain of Gcdh^-/- mice receiving high Lys. These data support the hypothesis that low Lys diet is beneficial in GA I by preventing redox imbalance, whereas a high Lys diet or systemic inflammation per se or combined induce oxidative stress in striatum and cerebral cortex that are mainly damaged in this disorder.

l-Carnitine prevents oxidative stress in striatum of glutaryl-CoA dehydrogenase deficient mice submitted to lysine overload

The deficiency of the enzyme glutaryl-CoA dehydrogenase leads to predominant accumulation of glutaric acid (GA) in the organism and is known as glutaric acidemia type I (GA1). Despite the mechanisms of brain damage involved in GA1 are not fully understood, oxidative stress may be involved in this process. Treatment is based on protein/lysine (Lys) restriction and l-carnitine (L-car) supplementation. L-car was recently shown to have an important antioxidant role. A knockout mice model (Gcdh^-/-) submitted to a dietary overload of Lys was developed to better understand the GA1 pathogenesis. In this study, we evaluated L-car and glutarylcarnitine levels, the lipid and protein damage, reactive oxygen species (ROS) production and antioxidant enzymes activities in striatum of Gcdh^-/- and wild-type (WT) mice. We also determined the effect of the L-car treatment on these parameters. Thirty-day-old Gcdh^-/- and WT mice were fed a normal chow (0.9% Lys) or submitted to a high Lys diet (4.7%) for 72 h. Additionally, these animals were administered with three intraperitoneal injections of saline or L-car in different times. Gcdh^-/- mice were deficient in L-car and presented a higher glutarylcarnitine levels. They also presented lipid and protein damage, an increased ROS production and altered antioxidant enzymes compared to WT mice. Additionally, mice exposed to Lys overload presented higher alterations in these parameters than mice under normal diet, which were significantly decreased or normalized in those receiving L-car. Thus, we demonstrated a new beneficial effect of the L-car treatment attenuating or abolishing the oxidative stress process in Gcdh^-/- mice.

Anandamide Reduces the Toxic Synergism Exerted by Quinolinic Acid and Glutaric Acid in Rat Brain Neuronal Cells

The endocannabinoid system (ECS) regulates several physiological processes in the Central Nervous System, including the modulation of neuronal excitability via activation of cannabinoid receptors (CBr). Both glutaric acid (GA) and quinolinic acid (QUIN) are endogenous metabolites that, under pathological conditions, recruit common toxic mechanisms. A synergistic effect between them has already been demonstrated, supporting potential implications for glutaric acidemia type I (GA I). Here we investigated the possible involvement of a cannabinoid component in the toxic model exerted by QUIN + GA in rat cortical slices and primary neuronal cell cultures. The effects of the CB1 receptor agonist anandamide (AEA), and the fatty acid amide hydrolase inhibitor URB597, were tested on cell viability in cortical brain slices and primary neuronal cultures exposed to QUIN, GA, or QUIN + GA. As a pre-treatment to the QUIN + GA condition, AEA prevented the loss of cell viability in both preparations. URB597 only protected in a moderate manner the cultured neuronal cells against the QUIN + GA-induced damage. The use of the CB1 receptor reverse agonist AM251 in both biological preparations prevented partially the protective effects exerted by AEA, thus suggesting a partial role of CB1 receptors in this toxic model. AEA also prevented the cell damage and apoptotic death induced by the synergic model in cell cultures. Altogether, these findings demonstrate a modulatory role of the ECS on the synergic toxic actions exerted by QUIN + GA, thus providing key information for the understanding of the pathophysiological events occurring in GA I.

Involvement of the Cholinergic Parameters and Glial Cells in Learning Delay Induced by Glutaric Acid: Protection by N-Acetylcysteine

Dysfunction of basal ganglia neurons is a characteristic of glutaric acidemia type I (GA-I), an autosomal recessive inherited neurometabolic disease characterized by deficiency of glutaryl-CoA dehydrogenase (GCDH) and accumulation of glutaric acid (GA). The affected patients present clinical manifestations such as motor dysfunction and memory impairment followed by extensive striatal neurodegeneration. Knowing that there is relevant striatal dysfunction in GA-I, the purpose of the present study was to verify the performance of young rats chronically injected with GA in working and procedural memory test, and whether N-acetylcysteine (NAC) would protect against impairment induced by GA. Rat pups were injected with GA (5 μmol g body weight^-1, subcutaneously; twice per day; from the 5th to the 28th day of life) and were supplemented with NAC (150 mg/kg/day; intragastric gavage; for the same period). We found that GA injection caused delay procedural learning; increase of cytokine concentration, oxidative markers, and caspase levels; decrease of antioxidant defenses; and alteration of acetylcholinesterase (AChE) activity. Interestingly, we found an increase in glial cell immunoreactivity and decrease in the immunoreactivity of nuclear factor-erythroid 2-related factor 2 (Nrf2), nicotinic acetylcholine receptor subunit alpha 7 (α7nAChR), and neuronal nuclei (NeuN) in the striatum. Indeed, NAC administration improved the cognitive performance, ROS production, neuroinflammation, and caspase activation induced by GA. NAC did not prevent neuronal death, however protected against alterations induced by GA on Iba-1 and GFAP immunoreactivities and AChE activity. Then, this study suggests possible therapeutic strategies that could help in GA-I treatment and the importance of the striatum in the learning tasks.

Oxidative damage in glutaric aciduria type I patients and the protective effects of l-carnitine treatment

The deficiency of the enzyme glutaryl-CoA dehydrogenase, known as glutaric acidemia type I (GA-I), leads to the accumulation of glutaric acid (GA) and glutarilcarnitine (C5DC) in the tissues and body fluids, unleashing important neurotoxic effects. l-carnitine (l-car) is recommended for the treatment of GA-I, aiming to induce the excretion of toxic metabolites. l-car has also demonstrated an important role as antioxidant and anti-inflammatory in some neurometabolic diseases. This study evaluated GA-I patients at diagnosis moment and treated the oxidative damage to lipids, proteins, and the inflammatory profile, as well as in vivo and in vitro DNA damage, reactive nitrogen species (RNS), and antioxidant capacity, verifying if the actual treatment with l-car (100 mg kg^-1  day^-1 ) is able to protect the organism against these processes. Significant increases of GA and C5DC were observed in GA-I patients. A deficiency of carnitine in patients before the supplementation was found. GA-I patients presented significantly increased levels of isoprostanes, di-tyrosine, urinary oxidized guanine species, and the RNS, as well as a reduced antioxidant capacity. The l-car supplementation induced beneficial effects reducing these biomarkers levels and increasing the antioxidant capacity. GA, in three different concentrations, significantly induced DNA damage in vitro, and the l-car was able to prevent this damage. Significant increases of pro-inflammatory cytokines IL-6, IL-8, GM-CSF, and TNF-α were shown in patients. Thus, the beneficial effects of l-car presented in the treatment of GA-I are due not only by increasing the excretion of accumulated toxic metabolites, but also by preventing oxidative damage.

Global metabolomic responses in urine from atm deficient mice in response to LD50/30 gamma irradiation doses

Exposures to ionizing radiation (IR) may either be accidental or intentional, for medical purposes or even through terrorist actions. As certain populations emerge to be more radiosensitive than others, it is imperative to assess those individuals and treat them accordingly. To demonstrate the feasibility of rapid identification of such cases, we utilized the highly radiosensitive mouse model Atm-/- in the C57BL/6 background, and evaluated the urinary responses in 8-10 week old male mice at early time points (4, 24, and 72 h) after exposure to their respective LD50/30 doses [4 Gy for Atm-/- , and 8 Gy for wild type (WT)]. Urinary profiles from heterozygous animals exhibited remarkably similar responses to WT before and after radiation exposure. However, genotypic differences (WT or Atm-/- ) were the primary driver to responses to radiation. Putative metabolites were validated through tandem mass spectrometry and included riboflavin, uric acid, d-ribose, d-glucose, pantothenic acid, taurine, kynurenic acid, xanthurenic acid, 2-oxoadipic acid, glutaric acid, 5'-deoxy-5'-methylthioadenosine, and hippuric acid. These metabolites mapped to several interconnected metabolic pathways which suggest that radiosensitive mouse models have underlying differences significantly impacting overall metabolism. This was further amplified by ionizing radiation at different time points. This study further emphasizes that genetically based radiosensitivity is reflected in the metabolic processes, and can be directly observed in urine. These differences in turn can potentially be used to identify individuals that may require altered medical treatment in an emergency radiological situation or modification of a regimen during a radiotherapy session. Environ. Mol. Mutagen. 59:576-585, 2018. © 2018 Wiley Periodicals, Inc.

The Role of Gut Microbiota and Diet on Uremic Retention Solutes Production in the Context of Chronic Kidney Disease

Uremic retention solutes (URS) are associated with cardiovascular complications and poor survival in chronic kidney disease. The better understanding of the origin of a certain number of these toxins enabled the development of new strategies to reduce their production. URS can be classified according to their origins (i.e., host, microbial, or exogenous). The discovery of the fundamental role that the intestinal microbiota plays in the production of many URS has reinstated nutrition at the heart of therapeutics to prevent the accumulation of URS and their deleterious effects. The intestinal microbiota is personalized and is strongly influenced by dietary habits, such as the quantity and the quality of dietary protein and fibers. Herein, this review out lines the role of intestinal microbiota on URS production and the recent discoveries on the effect of diet composition on the microbial balance in the host with a focus on the effect on URS production.

Altered Redox Homeostasis in Branched-Chain Amino Acid Disorders, Organic Acidurias, and Homocystinuria

Inborn errors of metabolism (IEMs) are a group of monogenic disorders characterized by dysregulation of the metabolic networks that underlie development and homeostasis. Emerging evidence points to oxidative stress and mitochondrial dysfunction as major contributors to the multiorgan alterations observed in several IEMs. The accumulation of toxic metabolites in organic acidurias, respiratory chain, and fatty acid oxidation disorders inhibits mitochondrial enzymes and processes resulting in elevated levels of reactive oxygen species (ROS). In other IEMs, as in homocystinuria, different sources of ROS have been proposed. In patients' samples, as well as in cellular and animal models, several studies have identified significant increases in ROS levels along with decreases in antioxidant defences, correlating with oxidative damage to proteins, lipids, and DNA. Elevated ROS disturb redox-signaling pathways regulating biological processes such as cell growth, differentiation, or cell death; however, there are few studies investigating these processes in IEMs. In this review, we describe the published data on mitochondrial dysfunction, oxidative stress, and impaired redox signaling in branched-chain amino acid disorders, other organic acidurias, and homocystinuria, along with recent studies exploring the efficiency of antioxidants and mitochondria-targeted therapies as therapeutic compounds in these diseases.

Toxic Synergism Between Quinolinic Acid and Glutaric Acid in Neuronal Cells Is Mediated by Oxidative Stress: Insights to a New Toxic Model

It has been shown that synergistic toxic effects of quinolinic acid (QUIN) and glutaric acid (GA), both in isolated nerve endings and in vivo conditions, suggest the contribution of these metabolites to neurodegeneration. However, this synergism still requires a detailed characterization of the mechanisms involved in cell damage during its occurrence. In this study, the effects of subtoxic concentrations of QUIN and/or GA were tested in neuronal cultures, co-cultures (neuronal cells + astrocytes), and mixed cultures (neuronal cells + astrocytes + microglia) from rat cortex and striatum. The exposure of different cortical and striatal cell cultures to QUIN + GA resulted in cell death and stimulated different markers of oxidative stress, including reactive oxygen species (ROS) formation; changes in the activity of antioxidant enzymes such as superoxide dismutase, catalase, and glutathione peroxidase; and depletion of endogenous antioxidants such as -SH groups and glutathione. The co-incubation of neuronal cultures with QUIN + GA plus the N-methyl-D-aspartate antagonist MK-801 prevented cell death but not ROS formation, whereas the antioxidant melatonin reduced both parameters. Our results demonstrated that QUIN and GA can create synergistic scenarios, inducing toxic effects on some parameters of cell viability via the stimulation of oxidative damage. Therefore, it is likely that oxidative stress may play a major causative role in the synergistic actions exerted by QUIN + GA in a variety of cell culture conditions involving the interaction of different neural types.

Higher Vulnerability of Menadione-Exposed Cortical Astrocytes of Glutaryl-CoA Dehydrogenase Deficient Mice to Oxidative Stress, Mitochondrial Dysfunction, and Cell Death: Implications for the Neurodegeneration in Glutaric Aciduria Type I

Patients affected by glutaric aciduria type I (GA-I) show progressive cortical leukoencephalopathy whose pathogenesis is poorly known. In the present work, we exposed cortical astrocytes of wild-type (Gcdh ^+/+ ) and glutaryl-CoA dehydrogenase knockout (Gcdh ^-/- ) mice to the oxidative stress inducer menadione and measured mitochondrial bioenergetics, redox homeostasis, and cell viability. Mitochondrial function (MTT and JC1-mitochondrial membrane potential assays), redox homeostasis (DCFH oxidation, nitrate and nitrite production, GSH concentrations and activities of the antioxidant enzymes SOD and GPx), and cell death (propidium iodide incorporation) were evaluated in primary cortical astrocyte cultures of Gcdh ^+/+ and Gcdh ^-/- mice unstimulated and stimulated by menadione. We also measured the pro-inflammatory response (TNFα levels, IL1-β and NF-ƙB) in unstimulated astrocytes obtained from these mice. Gcdh ^-/- mice astrocytes were more vulnerable to menadione-induced oxidative stress (decreased GSH concentrations and altered activities of the antioxidant enzymes), mitochondrial dysfunction (decrease of MTT reduction and JC1 values), and cell death as compared with Gcdh ^+/+ astrocytes. A higher inflammatory response (TNFα, IL1-β and NF-ƙB) was also observed in Gcdh ^-/- mice astrocytes. These data indicate a higher susceptibility of Gcdh ^-/- cortical astrocytes to oxidative stress and mitochondrial dysfunction, probably leading to cell death. It is presumed that these pathomechanisms may contribute to the cortical leukodystrophy observed in GA-I patients.

Oxidative Stress, Disrupted Energy Metabolism, and Altered Signaling Pathways in Glutaryl-CoA Dehydrogenase Knockout Mice: Potential Implications of Quinolinic Acid Toxicity in the Neuropathology of Glutaric Acidemia Type I

We investigated the effects of an acute intrastriatal QUIN administration on cellular redox and bioenergetics homeostasis, as well as on important signaling pathways in the striatum of wild-type (Gcdh ^+/+ , WT) and knockout mice for glutaryl-CoA dehydrogenase (Gcdh ^-/- ) fed a high lysine (Lys, 4.7 %) chow. QUIN increased lactate release in both Gcdh ^+/+ and Gcdh ^-/- mice and reduced the activities of complex IV and creatine kinase only in the striatum of Gcdh ^-/- mice. QUIN also induced lipid and protein oxidative damage and increased the generation of reactive nitrogen species, as well as the activities of the antioxidant enzymes glutathione peroxidase, superoxide dismutase 2, and glutathione-S-transferase in WT and Gcdh ^-/- animals. Furthermore, QUIN induced DCFH oxidation (reactive oxygen species production) and reduced GSH concentrations (antioxidant defenses) in Gcdh ^-/- . An early increase of Akt and phospho-Erk 1/2 in the cytosol and Nrf2 in the nucleus was also observed, as well as a decrease of cytosolic Keap1caused by QUIN, indicating activation of the Nrf2 pathway mediated by Akt and phospho-Erk 1/2, possibly as a compensatory protective mechanism against the ongoing QUIN-induced toxicity. Finally, QUIN increased NF-κB and diminished IκBα expression, evidencing a pro-inflammatory response. Our data show a disruption of energy and redox homeostasis associated to inflammation induced by QUIN in the striatum of Gcdh ^-/- mice submitted to a high Lys diet. Therefore, it is presumed that QUIN may possibly contribute to the pathophysiology of striatal degeneration in children with glutaric aciduria type I during inflammatory processes triggered by infections or vaccinations.

Experimental evidence that overexpression of NR2B glutamate receptor subunit is associated with brain vacuolation in adult glutaryl-CoA dehydrogenase deficient mice: A potential role for glutamatergic-induced excitotoxicity in GA I neuropathology

Glutaric aciduria type I (GA I) is biochemically characterized by accumulation of glutaric and 3-hydroxyglutaric acids in body fluids and tissues, particularly in the brain. Affected patients show progressive cortical leukoencephalopathy and chronic degeneration of the basal ganglia whose pathogenesis is still unclear. In the present work we investigated parameters of bioenergetics and redox homeostasis in various cerebral structures (cerebral cortex, striatum and hippocampus) and heart of adult wild type (Gcdh(+/+)) and glutaryl-CoA dehydrogenase deficient knockout (Gcdh(-/-)) mice fed a baseline chow. Oxidative stress parameters were also measured after acute lysine overload. Finally, mRNA expression of NMDA subunits and GLT1 transporter was determined in cerebral cortex and striatum of these animals fed a baseline or high lysine (4.7%) chow. No significant alterations of bioenergetics or redox status were observed in these mice. In contrast, mRNA expression of the NR2B glutamate receptor subunit and of the GLT1 glutamate transporter was higher in cerebral cortex of Gcdh(-/-) mice. Furthermore, NR2B expression was markedly elevated in striatum of Gcdh(-/-) animals receiving chronic Lys overload. These data indicate higher susceptibility of Gcdh(-/-) mice to excitotoxic damage, implying that this pathomechanism may contribute to the cortical and striatum alterations observed in GA I patients.

Fasting but not changes of plasma metabolome during oral glucose tolerance tests improves the diagnosis of severe coronary arterial stenosis

BACKGROUND

Noninvasive stress tests for the diagnosis of significant coronary arterial stenosis requiring intervention are not perfect. We investigated whether plasma metabolome during the oral glucose tolerance test (OGTT) can improve the diagnosis.

METHODS

A total of 117 subjects with positive stress test results who received coronary angiography were recruited. After excluding subjects with a history of myocardial infarction and subjects who did not receive OGTT, the 18 subjects without significant stenosis were selected as controls. Another 18 age- and sex-matched subjects with significant stenosis were selected as cases. Plasma metabolome from samples obtained in fasting, 30 and 120 min after OGTT was measured using liquid chromatography combined with time-of-flight mass spectrometry.

RESULTS

We found five metabolites which can identify patients with significant stenosis independent to clinical risk factors, including diabetes, hypertension, hypercholesterolaemia, smoking and history of percutaneous coronary intervention (all P < 0·05). The area under the receiver operating characteristic (AUROC) curve of these metabolites was 0·799-0·818 at fasting and 30 min after OGTT. The addition of metabolites to clinical factors increases the AUROC (0·616, 95%CI 0·429-0·803 for model with clinical factors only; 0·824, 95%CI 0·689-0·959 for model with four metabolites and clinical factors). The changes of plasma metabolite levels during OGTT did not significantly improve the diagnostic performance.

CONCLUSIONS

Fasting plasma metabolome, but not change of plasma metabolome during OGTT, can improve the diagnosis of significant stenosis in patients with positive noninvasive stress test results.

Glutaric acid-mediated apoptosis in primary striatal neurons

Glutaric acid (GA) has been implicated in the mechanism of neurodegeneration in glutaric aciduria type I. In the present study, the potential cytotoxic effects of GA (0.1~50 mM for 24~96 h) were examined in cultured primary rat striatal neurons. Results showed increase in the number of cells labeled by annexin-V or with apoptotic features shown by Hoechst/PI staining and transmission electron microscopy (TEM) and upregulation of the expression of mRNA as well as the active protein fragments caspase 3, suggesting involvement of the caspase 3-dependent apoptotic pathway in GA-induced striatal neuronal death. This effect was in part suppressed by the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 but not the α -amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) antagonist 6-cyano-7-nitroquinoxalone-2,3-dione (CNQX). Thus, GA may trigger neuronal damage partially through apoptotic pathway and via activation of NMDA receptors in cultured primary striatal neurons.

Increased glutamate receptor and transporter expression in the cerebral cortex and striatum of gcdh-/- mice: possible implications for the neuropathology of glutaric acidemia type I

We determined mRNA expression of the ionotropic glutamate receptors NMDA (NR1, NR2A and NR2B subunits), AMPA (GluR2 subunit) and kainate (GluR6 subunit), as well as of the glutamate transporters GLAST and GLT1 in cerebral cortex and striatum of wild type (WT) and glutaryl-CoA dehydrogenase deficient (Gchh^-/-) mice aged 7, 30 and 60 days. The protein expression levels of some of these membrane proteins were also measured. Overexpression of NR2A and NR2B in striatum and of GluR2 and GluR6 in cerebral cortex was observed in 7-day-old Gcdh^-/-. There was also an increase of mRNA expression of all NMDA subunits in cerebral cortex and of NR2A and NR2B in striatum of 30-day-old Gcdh^-/- mice. At 60 days of life, all ionotropic receptors were overexpressed in cerebral cortex and striatum of Gcdh^-/- mice. Higher expression of GLAST and GLT1 transporters was also verified in cerebral cortex and striatum of Gcdh^-/- mice aged 30 and 60 days, whereas at 7 days of life GLAST was overexpressed only in striatum from this mutant mice. Furthermore, high lysine intake induced mRNA overexpression of NR2A, NR2B and GLAST transcripts in striatum, as well as of GluR2 and GluR6 in both striatum and cerebral cortex of Gcdh^-/- mice. Finally, we found that the protein expression of NR2A, NR2B, GLT1 and GLAST were significantly greater in cerebral cortex of Gcdh^-/- mice, whereas NR2B and GLT1 was similarly enhanced in striatum, implying that these transcripts were translated into their products. These results provide evidence that glutamate receptor and transporter expression is higher in Gcdh^-/- mice and that these alterations may be involved in the pathophysiology of GA I and possibly explain, at least in part, the vulnerability of striatum and cerebral cortex to injury in patients affected by GA I.

Effect of acute administration of L-tyrosine on oxidative stress parameters in brain of young rats

Tyrosinemia type II, also known as Richner-Hanhart syndrome, is an autosomal recessive inborn error of metabolism caused by a deficiency of hepatic cytosolic tyrosine aminotransferase, and is associated with neurologic and development difficulties in numerous patients. Considering that the mechanisms underlying the neurological dysfunction in hypertyrosinemic patients are poorly known and that studies demonstrated that high concentrations of tyrosine provoke oxidative stress in vitro and in vivo in the cerebral cortex of rats, in the present study we investigate the oxidative stress parameters (enzymatic antioxidant defenses, thiobarbituric acid-reactive substances and protein carbonyl content) in cerebellum, hippocampus and striatum of 30-old-day rats after acute administration of L-tyrosine. Our results demonstrated that the acute administration of L-tyrosine increased the thiobarbituric acid reactive species levels in hippocampus and the carbonyl levels in cerebellum, hippocampus and striatum. In addition, acute administration of L-tyrosine significantly decreased superoxide dismutase activity in cerebellum, hippocampus and striatum, while catalase was increased in striatum. In conclusion, the oxidative stress may contribute, along with other mechanisms, to the neurological dysfunction characteristic of hypertyrosinemia and the administration of antioxidants may be considered as a potential adjuvant therapy for tyrosinemia, especially type II.

Neurotoxic effects of trans-glutaconic acid in rats

trans-Glutaconic acid (tGA) is an unsaturated C5-dicarboxylic acid which may be found accumulated in glutaric aciduria type I, whose pathophysiology is still uncertain. In the present work it was investigated the in vitro effect of increasing tGA concentrations on neurochemical and oxidative stress parameters in rat cerebral cortex. We observed that Na⁺, K⁺-ATPase activity was reduced by tGA, but not creatine kinase, respiratory chain complex IV, and ATP synthase activities. On the other hand, tGA significantly increased lipid peroxidation (thiobarbituric acid-reactive species levels and spontaneous chemiluminescence), as well as protein oxidative damage (oxidation of sulfhydryl groups). tGA also significantly decreased nonenzymatic antioxidant defenses (TRAP and reduced glutathione levels). Our data suggest that tGA may be neurotoxic in rat brain.

Disruption of brain redox homeostasis in glutaryl-CoA dehydrogenase deficient mice treated with high dietary lysine supplementation

Deficiency of glutaryl-CoA dehydrogenase (GCDH) activity or glutaric aciduria type I (GA I) is an inherited neurometabolic disorder biochemically characterized by predominant accumulation of glutaric acid and 3-hydroxyglutaric acid in the brain and other tissues. Affected patients usually present acute striatum necrosis during encephalopathic crises triggered by metabolic stress situations, as well as chronic leukodystrophy and delayed myelination. Considering that the mechanisms underlying the brain injury in this disease are not yet fully established, in the present study we investigated important parameters of oxidative stress in the brain (cerebral cortex, striatum and hippocampus), liver and heart of 30-day-old GCDH deficient knockout (Gcdh(-/-)) and wild type (WT) mice submitted to a normal lysine (Lys) (0.9% Lys), or high Lys diets (2.8% or 4.7% Lys) for 60 h. It was observed that the dietary supplementation of 2.8% and 4.7% Lys elicited noticeable oxidative stress, as verified by an increase of malondialdehyde concentrations (lipid oxidative damage) and 2-7-dihydrodichlorofluorescein (DCFH) oxidation (free radical production), as well as a decrease of reduced glutathione levels and alteration of various antioxidant enzyme activities (antioxidant defenses) in the cerebral cortex and the striatum, but not in the hippocampus, the liver and the heart of Gcdh(-/-) mice, as compared to WT mice receiving the same diets. Furthermore, alterations of oxidative stress parameters in the cerebral cortex and striatum were more accentuated in symptomatic, as compared to asymptomatic Gcdh(-/-) mice exposed to 4.7% Lys overload. Histopathological studies performed in the cerebral cortex and striatum of these animals exposed to high dietary Lys revealed increased expression of oxidative stress markers despite the absence of significant structural damage. The results indicate that a disruption of redox homeostasis in the cerebral cortex and striatum of young Gcdh(-/-) mice exposed to increased Lys diet may possibly represent an important pathomechanism of brain injury in GA I patients under metabolic stress.

Reduction of Na+, K+-ATPase activity and expression in cerebral cortex of glutaryl-CoA dehydrogenase deficient mice: a possible mechanism for brain injury in glutaric aciduria type I

Mitochondrial dysfunction has been proposed to play an important role in the neuropathology of glutaric acidemia type I (GA I). However, the relevance of bioenergetics disruption and the exact mechanisms responsible for the cortical leukodystrophy and the striatum degeneration presented by GA I patients are not yet fully understood. Therefore, in the present work we measured the respiratory chain complexes activities I-IV, mitochondrial respiratory parameters state 3, state 4, the respiratory control ratio and dinitrophenol (DNP)-stimulated respiration (uncoupled state), as well as the activities of α-ketoglutarate dehydrogenase (α-KGDH), creatine kinase (CK) and Na+, K+-ATPase in cerebral cortex, striatum and hippocampus from 30-day-old Gcdh-/- and wild type (WT) mice fed with a normal or a high Lys (4.7%) diet. When a baseline (0.9% Lys) diet was given, we verified mild alterations of the activities of some respiratory chain complexes in cerebral cortex and hippocampus, but not in striatum from Gcdh-/- mice as compared to WT animals. Furthermore, the mitochondrial respiratory parameters and the activities of α-KGDH and CK were not modified in all brain structures from Gcdh-/- mice. In contrast, we found a significant reduction of Na(+), K(+)-ATPase activity associated with a lower degree of its expression in cerebral cortex from Gcdh-/- mice. Furthermore, a high Lys (4.7%) diet did not accentuate the biochemical alterations observed in Gcdh-/- mice fed with a normal diet. Since Na(+), K(+)-ATPase activity is required for cell volume regulation and to maintain the membrane potential necessary for a normal neurotransmission, it is presumed that reduction of this enzyme activity may represent a potential underlying mechanism involved in the brain swelling and cortical abnormalities (cortical atrophy with leukodystrophy) observed in patients affected by GA I.

Hepatoprotective, cardioprotective, and renal-protective effects of organic and conventional grapevine leaf extracts on Wistar rat tissues

The purpose of this study was to evaluate the beneficial effects of organic and conventional grapevine (Vitis labrusca L.) leaf extracts in reducing hydrogen peroxide-induced stress in the liver, heart and kidney of Wistar rats by measuring lipids and proteins damages (carbonyl assay), as well as the activity of the antioxidant enzymes superoxide dismutase and catalase. The preincubation with 5 mg/mL of organic and conventional grapevine (Vitis labrusca L.) leaf extracts prevented both lipids and proteins oxidative damages in all tissues analyzed. The organic leaf extract was able to restore superoxide dismutase (kidney and liver) and catalase (heart) activities, which were modified by the treatment with H(2)O(2). The conventional extract was able to restore only the catalase activity in liver and heart tissues. The beneficial effects of the V labrusca leaf extract shown in this study could probably be important for formulating dietary supplements, as well as for developing new ingredients with improved antioxidant properties from other plant sources.

Marked reduction of Na(+), K(+)-ATPase and creatine kinase activities induced by acute lysine administration in glutaryl-CoA dehydrogenase deficient mice

Glutaric acidemia type I (GA I) is an inherited neurometabolic disorder caused by a severe deficiency of the mitochondrial glutaryl-CoA dehydrogenase activity leading to accumulation of predominantly glutaric (GA) and 3-hydroxyglutaric (3HGA) acids in the brain and other tissues. Affected patients usually present with hypotonia and brain damage and acute encephalopathic episodes whose pathophysiology is not yet fully established. In this study we investigated important parameters of cellular bioenergetics in brain, heart and skeletal muscle from 15-day-old glutaryl-CoA dehydrogenase deficient mice (Gcdh(-/-)) submitted to a single intra-peritoneal injection of saline (Sal) or lysine (Lys - 8 μmol/g) as compared to wild type (WT) mice. We evaluated the activities of the respiratory chain complexes II, II-III and IV, α-ketoglutarate dehydrogenase (α-KGDH), creatine kinase (CK) and synaptic Na(+), K(+)-ATPase. No differences of all evaluated parameters were detected in the Gcdh(-/-) relatively to the WT mice injected at baseline (Sal). Furthermore, mild increases of the activities of some respiratory chain complexes (II-III and IV) were observed in heart and skeletal muscle of Gcdh(-/-) and WT mice after Lys administration. However, the most marked effects provoked by Lys administration were marked decreases of the activities of Na(+), K(+)-ATPase in brain and CK in brain and skeletal muscle of Gcdh(-/-) mice. In contrast, brain α-KGDH activity was not altered in WT and Gcdh(-/-) injected with Sal or Lys. Our results demonstrate that reduction of Na(+), K(+)-ATPase and CK activities may play an important role in the pathogenesis of the neurodegenerative changes in GA I.

Induction of oxidative stress in brain of glutaryl-CoA dehydrogenase deficient mice by acute lysine administration

In the present work we evaluated a variety of indicators of oxidative stress in distinct brain regions (striatum, cerebral cortex and hippocampus), the liver, and heart of 30-day-old glutaryl-CoA dehydrogenase deficient (Gcdh(-/-)) mice. The parameters evaluated included thiobarbituric acid-reactive substances (TBA-RS), 2-7-dihydrodichlorofluorescein (DCFH) oxidation, sulfhydryl content, and reduced glutathione (GSH) concentrations. We also measured the activities of the antioxidant enzymes glutathione peroxidase (GPx), glutathione reductase (GR), catalase (CAT), superoxide dismutase (SOD) and glucose-6-phosphate dehydrogenase (G6PD). Under basal conditions glutaric (GA) and 3-OH-glutaric (3OHGA) acids were elevated in all tissues of the Gcdh(-/-) mice, but were essentially absent in WT animals. In contrast there were no differences between WT and Gcdh(-/-) mice in any of the indicators or oxidative stress under basal conditions. Following a single intra-peritoneal (IP) injection of lysine (Lys) there was a moderate increase of brain GA concentration in Gcdh(-/-) mice, but no change in WT. Lys injection had no effect on brain 3OHGA in either WT or Gcdh(-/-) mice. The levels of GA and 3OHGA were approximately 40% higher in striatum compared to cerebral cortex in Lys-treated mice. In the striatum, Lys administration provoked a marked increase of lipid peroxidation, DCFH oxidation, SOD and GR activities, as well as significant reductions of GSH levels and GPx activity, with no alteration of sulfhydryl content, CAT and G6PD activities. There was also evidence of increased lipid peroxidation and SOD activity in the cerebral cortex, along with a decrease of GSH levels, but to a lesser extent than in the striatum. In the hippocampus only mild increases of SOD activity and DCFH oxidation were observed. In contrast, Lys injection had no effect on any of the parameters of oxidative stress in the liver or heart of Gcdh(-/-) or WT animals. These results indicate that in Gcdh(-/-) mice cerebral tissue, particularly the striatum, is at greater risk for oxidative stress than peripheral tissues following Lys administration.

m-Trifluoromethyl diphenyl diselenide attenuates glutaric acid-induced seizures and oxidative stress in rat pups: involvement of the γ-aminobutyric acidergic system

Glutaric acidemia type I (GA-I) is an inherited metabolic disease characterized by accumulation of glutaric acid (GA) and seizures. The intrastriatal GA administration in rats has been used as an animal model to mimic seizures presented by glutaric acidemic patients. m-Trifluoromethyl diphenyl diselenide, (m-CF(3) -C(6) H(4) Se)(2) , is an organoselenium compound that protects against seizures induced by pentylenetetrazole in mice. Thus, the aim of this study was to investigate whether (m-CF(3) -C(6) H(4) Se)(2) is effective against GA-induced seizures and oxidative stress in rat pups 21 days of age. Our findings demonstrate that (m-CF(3) -C(6) H(4) Se)(2) preadministration (50 mg/kg; p.o.) protected against the reduction in latency and the increased duration of GA (1.3 μmol/right striatum)-induced seizures in rat pups. In addition, (m-CF(3) -C(6) H(4) Se)(2) protected against the increase in reactive species generation and the reduction in antioxidant defenses glutathione peroxidase and glutathione S-transferase activities induced by GA. By contrast, no change in glutathione reductase or catalase activities was found. In addition, (m-CF(3) -C(6) H(4) Se)(2) was effective in protecting against inhibition of Na(+) ,K(+) -ATPase activity caused by GA in striatum of rat pups. This study showed for the first time that GA administration caused an increase in [(3) H]GABA uptake from striatum slices of rat pups and that (m-CF(3) -C(6) H(4) Se)(2) preadministration protected against this increase. A positive correlation between duration of seizures and [(3) H]GABA uptake levels was demonstrated. The results indicate that (m-CF(3) -C(6) H(4) Se)(2) protected against GA-induced seizures. Moreover, these findings suggest that the protection against oxidative stress, the inhibition of Na(+) ,K(+) -ATPase activity, and the increase in [(3) H]GABA uptake are possible mechanisms for the potential anticonvulsant action of (m-CF(3) -C(6) H(4) Se)(2).

Caspase-3 mediates apoptosis of striatal cells in GA I rat model

In previous study, glutaric acid (GA) induced apoptosis of primary striatal neuron in vitro. In order to investigate the neurotoxic effects of GA on neonatal rat corpus striatum and the possible mechanism, 34 male pups were randomly assigned to NS group, low dose GA (LGA, 5 μmol GA/g body weight) group and high dose GA (HGA, 10 μmol GA/g body weight) group. These pups were subcutaneously administered with three injections from postnatal day 3 to 22 at 7:30 am, 15:00 pm and 22:30 pm and killed 12 h after the last injection. Microscopic pathology in corpus striatum was evaluated by HE staining. The apoptotic cells were identified by TUNEL staining. The transcript levels of caspase-3, 8, 9, Bax, Bcl-2 were detected by using real-time PCR and the protein levels of procaspase-3 and the active fraction were evaluated by Western blotting. In LGA and HGA groups, ventricle collapse, cortical atrophy by a macroscope and interstitial edema, vacuolations, widened perivascular space of bilateral striatum by a microscope were observed. TUNEL assay revealed that the apoptotic cells were increased in LGA and HGA groups. The transcript of caspase-3 was up-regulated to 2.5 fold, accompanied by the up-regulation of caspase-9, Bax and down-regulation of Bcl-2. The protein levels of procaspase-3 and the active fraction were up-regulated in LGA and HGA groups. The rat model for GA I showed mitochondrial apoptotic pathway may be involved in the GA-induced striatal lesion. Further studies should be taken to investigate the underlying mechanisms.

The unsolved puzzle of neuropathogenesis in glutaric aciduria type I

Glutaric aciduria type I (GA-I) is a cerebral organic aciduria caused by deficiency of glutaryl-Co-A dehydrogenase (GCDH). GCDH deficiency leads to accumulation of glutaric acid (GA) and 3-hydroxyglutaric acid (3-OHGA), two metabolites that are believed to be neurotoxic, in brain and body fluids. The disorder usually becomes clinically manifest during a catabolic state (e.g. intercurrent illness) with an acute encephalopathic crisis that results in striatal necrosis and in a permanent dystonic-dyskinetic movement disorder. The results of numerous in vitro and in vivo studies have pointed to three main mechanisms involved in the metabolite-mediated neuronal damage: excitotoxicity, impairment of energy metabolism and oxidative stress. There is evidence that during a metabolic crisis GA and its metabolites are produced endogenously in the CNS and accumulate because of limiting transport mechanisms across the blood-brain barrier. Despite extensive experimental work, the relative contribution of the proposed pathogenic mechanisms remains unclear and specific therapeutic approaches have yet to be developed. Here, we review the experimental evidence and try to delineate possible pathogenetic models and approaches for future studies.

Disruption of mitochondrial homeostasis in organic acidurias: insights from human and animal studies

Organic acidurias or organic acidemias constitute a group of inherited disorders caused by deficient activity of specific enzymes of amino acids, carbohydrates or lipids catabolism, leading to large accumulation and excretion of one or more carboxylic (organic) acids. Affected patients usually present neurologic symptoms and abnormalities, sometimes accompanied by cardiac and skeletal muscle alterations, whose pathogenesis is poorly known. However, in recent years growing evidence has emerged indicating that mitochondrial dysfunction is directly or indirectly involved in the pathology of various organic acidemias. Mitochondrial impairment in some of these diseases are generally due to mutations in nuclear genes of the tricarboxylic acid cycle or oxidative phosphorylation, while in others it seems to result from toxic influences of the endogenous organic acids to the mitochondrion. In this minireview, we will briefly summarize the present knowledge obtained from human and animal studies showing that disruption of mitochondrial homeostasis may represent a relevant pathomechanism of tissue damage in selective organic acidemias. The discussion will focus on mitochondrial alterations found in patients affected by organic acidemias and by the deleterious effects of the accumulating organic acids on mitochondrial pathways that are crucial for ATP formation and transfer. The elucidation of the mechanisms of toxicity of these acidic compounds offers new perspectives for potential novel adjuvant therapeutic strategies in selected disorders of this group.

Neonatal astrocyte damage is sufficient to trigger progressive striatal degeneration in a rat model of glutaric acidemia-I

BACKGROUND

We have investigated whether an acute metabolic damage to astrocytes during the neonatal period may critically disrupt subsequent brain development, leading to neurodevelopmental disorders. Astrocytes are vulnerable to glutaric acid (GA), a dicarboxylic acid that accumulates in millimolar concentrations in Glutaric Acidemia I (GA-I), an inherited neurometabolic childhood disease characterized by degeneration of striatal neurons. While GA induces astrocyte mitochondrial dysfunction, oxidative stress and subsequent increased proliferation, it is presently unknown whether such astrocytic dysfunction is sufficient to trigger striatal neuronal loss.

METHODOLOGY/PRINCIPAL FINDINGS

A single intracerebroventricular dose of GA was administered to rat pups at postnatal day 0 (P0) to induce an acute, transient rise of GA levels in the central nervous system (CNS). GA administration potently elicited proliferation of astrocytes expressing S100β followed by GFAP astrocytosis and nitrotyrosine staining lasting until P45. Remarkably, GA did not induce acute neuronal loss assessed by FluoroJade C and NeuN cell count. Instead, neuronal death appeared several days after GA treatment and progressively increased until P45, suggesting a delayed onset of striatal degeneration. The axonal bundles perforating the striatum were disorganized following GA administration. In cell cultures, GA did not affect survival of either striatal astrocytes or neurons, even at high concentrations. However, astrocytes activated by a short exposure to GA caused neuronal death through the production of soluble factors. Iron porphyrin antioxidants prevented GA-induced astrocyte proliferation and striatal degeneration in vivo, as well as astrocyte-mediated neuronal loss in vitro.

CONCLUSIONS/SIGNIFICANCE

Taken together, these results indicate that a transient metabolic insult with GA induces long lasting phenotypic changes in astrocytes that cause them to promote striatal neuronal death. Pharmacological protection of astrocytes with antioxidants during encephalopatic crisis may prevent astrocyte dysfunction and the ineluctable progression of disease in children with GA-I.

Acute exposure of rabbits to diphenyl diselenide: a toxicological evaluation

The simple organoselenium compound diphenyl diselenide (PhSe)(2) is a promising new pharmacological agent. However, few toxicological evaluations of this molecule have been reported. We evaluated the effects of acute administration of (PhSe)(2) on toxicological parameters in rabbits. Adult New Zealand rabbits were exposed to (PhSe)(2) (5-500 micromol kg(-1) , intraperitoneally) once a day for 5 days. Exposure to 500 micromol kg(-1) caused 85% mortality. Exposure to 50 micromol kg(-1) of (PhSe)(2) increased the glutathione levels in the hippocampus, kidney, heart, muscle and blood, whereas lipoperoxidation (TBARS) decreased in the cerebellum and kidney after exposure to 5 micromol kg(-1) . The activity of glutathione peroxidase increased in the heart and muscle of rabbits treated with 50 micromol kg(-1) of (PhSe)(2) and glutathione reductase activity was reduced in the cerebellum, cerebral cortex and kidney. Treatment with (PhSe)(2) reduced the activity of δ-aminolevulinate dehydratase in the hippocampus and increased this activity in the heart, but did not alter the activity of complexes I and II of the respiratory chain in the liver and brain. Hepatic and renal biochemical and histological parameters were not modified by (PhSe)(2) and apoptosis was not detected in these tissues; however, the hepatic cells tended to accumulate fat vacuoles. These results indicated that acute toxicology to (PhSe)(2) in rabbit is dependent on the dose, which should motivate further experiments on the therapeutic properties of this compound.

Induction of S100B secretion in C6 astroglial cells by the major metabolites accumulating in glutaric acidemia type I

Glutaryl-CoA dehydrogenase deficiency or glutaric acidemia type I (GA I) is an inherited neurometabolic disorder biochemically characterized by tissue accumulation of predominantly glutaric (GA) and 3-hydroxyglutaric (3OHGA) acids and clinically by severe neurological symptoms and structural brain abnormalities, manifested as progressive cerebral atrophy and acute striatum degeneration following encephalopathic crises, whose pathophysiology is still in debate. Considering that reactive astrogliosis is a common finding in brain of GA I patients, in the present study we investigated the effects of GA and 3OHGA on glial activity determined by S100B release by rat C6-glioma cells. We also evaluated the effects of these organic acids on some parameters of oxidative stress in these astroglial cells. We observed that GA and 3OHGA significantly increased S100B secretion and thiobarbituric acid-reactive substances (lipid peroxidation), whereas GA markedly decreased reduced glutathione levels in these glioma cells. This is the first report demonstrating that the major metabolites accumulating in GA I activate S100B secretion in astroglial cells, indicating activation of these cells. We also showed that GA and 3OHGA induced oxidative stress in C6 lineage cells, confirming previous findings observed in brain fresh tissue. It is therefore presumed that reactive glial cells and oxidative damage may underlie at least in part the neuropathology of GA I.

Evidence for oxidative stress in tissues derived from succinate semialdehyde dehydrogenase-deficient mice

Animal models of inborn errors of metabolism are useful for investigating the pathogenesis associated with the corresponding human disease. Since the mechanisms involved in the pathophysiology of succinate semialdehyde dehydrogenase (SSADH) deficiency (Aldh5a1; OMIM 271980) are still not established, in the present study we evaluated the tissue antioxidant defences and lipid peroxidation in various cerebral structures (cortex, cerebellum, thalamus and hippocampus) and in the liver of SSADH-deficient mice. The parameters analysed were total radical-trapping antioxidant potential (TRAP) and glutathione (GSH) levels, the activities of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), as well as thiobarbituric acid-reactive substances (TBARS). We first observed that the tissue nonenzymatic antioxidant defences were significantly reduced in the SSADH-deficient animals, particularly in the liver (decreased TRAP and GSH) and in the cerebral cortex (decreased GSH), as compared to the wild-type mice. Furthermore, SOD activity was significantly increased in the liver and cerebellum, whereas the activity of CAT was significantly higher in the thalamus. In contrast, GPx activity was significantly diminished in the hippocampus. Finally, we observed that lipid peroxidation (TBARS levels) was markedly increased in the liver and cerebral cortex, reflecting a high lipid oxidative damage in these tissues. Our data showing an imbalance between tissue antioxidant defences and oxidative attack strongly indicate that oxidative stress is involved in the pathophysiology of SSADH deficiency in mice, and likely the corresponding human disorder.