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J Krieglstein

Publications and source records attributed to J Krieglstein.

At least 73 records · Page 4Linked to original sources
PubMed1997

Blockade of calpain proteolytic activity rescues neurons from glutamate excitotoxicity.

The potential of protease inhibitors E-64, calpain inhibitor I (CPI-I) and MDL28170 to protect hippocampal neurons in an in vitro model of neurotoxicity was investigated. Hippocampal cultures were treated with glutamate, and neurotoxicity was quantified. Glutamate treated cultures exhibited damage to approximately 50% of neurons. In contrast only 20-30% of neurons were damaged in cultures treated with glutamate and calpain inhibitors. E-64 and CPI-I are capable of protecting neurons from injury only in pre-treatment schedule. MDL28170 exhibits a neuroprotective effect in the pre-treatment schedule and also even when given immediately after the cultures had been switched to the glutamate-containing medium. Although the neuroprotective effect of MDL28170 in the postreatment schedule was modest, this supports a strick link between the ability of protease inhibitors to penetrate cellular membranes and their potency of neuroprotection. These data provide evidence that calpain-induced proteolysis is an important pathogenic factor in brain injury and suggest that calpain inhibitors may be considered as a powerful mean to counteract the sequelea of neurotoxicity.

Animals↗
PubMed1997

Differential effects of scopolamine on neuronal survival in ischemia and glutamate neurotoxicity: relationships to the excessive vulnerability of the dorsoseptal hippocampus.

The neurodegeneration in the CA1 subfield of hippocampus exhibited a dorsal-ventral gradient of susceptibility in global ischemia (82% dorsoseptally and only 16% ventrotemporally). Scopolamine (SCOP) did not improve the neuronal damage caused by the global ischemic challenge in rats and did not reduce the infarct area after the focal MCA-occlusion in mice. No differences were observed between saline and SCOP-treated animals in the physiologic parameters, except for a slight increase in rectal temperature. In contrast, treatment of hippocampal cultures with increasing concentrations of SCOP (1 nM to 1 mM) under glutamate incubation had a beneficial effect on neuronal viability. These data show that (1) there is substantial gradient of vulnerability of the hippocampus from dorsal to ventral in global ischemia and (2) that interactions between the NMDA, muscarinic receptors and their corresponding neurotransmitter inputs to hippocampal neurons are evident in vitro and may play a crucial role in neuronal neurodegeneration. However, the mechanisms underlying the high vulnerability of dorsal hippocampus still remain enigmatic.

Animals↗
PubMed1997

Influence of flupirtine on a G-protein coupled inwardly rectifying potassium current in hippocampal neurones.

1. Previous studies have shown that flupirtine, a centrally acting, non-opioid analgesic agent, also exhibits neuroprotective activity in focal cerebral ischaemia in mice and reduces apoptosis induced by NMDA, gp 120 of HIV, prior protein fragment or lead acetate as well as necrosis induced by glutamate or NMDA in cell culture. To study the potential mechanism of the neuroprotective action of flupirtine, we investigated whether flupirtine is able to modulate potassium or NMDA-induced currents in rat cultured hippocampal neurones by use of the whole-cell configuration of the patch-clamp technique. 2. We demonstrated that 1 microM flupirtine activated an inwardly rectifying potassium current (K(ir)) in hippocampal neurones (deltaI=-39+/-18 pA at -130 mV; n=10). This effect was dose-dependent (EC50=0.6 microM). The reversal potential for K(ir) was in agreement with the potassium equilibrium potential predicted from the Nernst equation showing that K(ir) was predominantly carried by K+. Furthermore, the induced current was blocked completely by Ba2+ (1 mM), an effect typical for K(ir). 3. The activation of K(ir) by flupirtine was largely prevented by pretreatment of the cells with pertussis toxin (PTX) indicating the involvement of a PTX-sensitive G-protein in the transduction mechanism (deltaI=-3+/-6 pA at -130 mV; n=8). Inclusion of cyclic AMP in the intracellular solution completely abolished the activation of K(ir) (n=7). 4. The selective alpha2-adrenoceptor antagonist SKF-86466 (10 microM), the selective 5-HT1A antagonist NAN 190 as well as the selective GABA(B) antagonist 2-hydroxysaclofen (10 microM) failed to block the flupirtine effect on the inward rectifier. 5. Flupirtine (1 microM) could not change the current induced by 50 microM NMDA. 6. These results show that in cultured hippocampal neurones flupirtine activates an inwardly rectifying potassium current and that a PTX-sensitive G-protein is involved in the transduction mechanism.

Aminopyridines↗
PubMed1997

Ca2+ and reactive oxygen species in staurosporine-induced neuronal apoptosis.

Staurosporine (0.03-0.5 microM) induced a dose-dependent, apoptotic degeneration in cultured rat hippocampal neurons that was sensitive to 24-h pretreatments with the protein synthesis inhibitor cycloheximide (1 microM) or the cell cycle inhibitor mimosine (100 microM). To investigate the role of Ca2+ and reactive oxygen species in staurosporine-induced neuronal apoptosis, we overexpressed calbindin D28K, a Ca2+ binding protein, and Cu/ Zn superoxide dismutase, an antioxidative enzyme, in the hippocampal neurons using adenovirus-mediated gene transfer. Infection of the cultures with the recombinant adenoviruses (100 multiplicity of infection) resulted in a stable expression of the respective proteins assessed 48 h later. Overexpression of both calbindin D28K and Cu/Zn superoxide dismutase significantly reduced staurosporine neurotoxicity compared with control cultures infected with a beta-galactosidase overexpressing adenovirus. Staurosporine-induced neuronal apoptosis was also significantly reduced when the culture medium was supplemented with 10 or 30 mM K+, suggesting that Ca2+ influx via voltage-sensitive Ca2+ channels reduces this apoptotic cell death. In contrast, neither the glutamate receptor agonist NMDA (1-10 microM) nor the NMDA receptor antagonist dizocilpine (MK-801; 1 microM) was able to reduce staurosporine neurotoxicity. Cultures treated with the antioxidants U-74500A (1-10 microM) and N-acetylcysteine (100 microM) also demonstrated reduced staurosporine neurotoxicity. These results suggest a fundamental role for both Ca2+ and reactive oxygen species in staurosprine-induced neuronal apoptosis.

Animals↗
PubMed1997

Regional cerebral glucose utilization in immature fetal guinea pigs during maternal isocapnic hypoxemia.

Recent studies in immature fetal animals demonstrated only a slight or variable increase in the cerebral glycolytic rate during moderate isocapnic hypoxemia. However, the methods used in those studies did not allow for detection of small differences or of regional redistributions of the cerebral glycolytic rate. Hence, a global increase or a regional redistribution of the cerebral glycolytic rate during hypoxemia accompanied by a severe increase in tissue lactate concentration in a few brain areas may have been overlooked in these studies. Because these pathophysiologic mechanisms seem to considerably exacerbate neuronal cell damage due to hypoxic/ischemic insults, we were keen to clarify this point. We, therefore, applied the 2-deoxyglucose method to fetal guinea pigs in utero and measured total and regional cerebral glucose utilization in fetuses of this species at 0.75 of gestation during maternal isocapnic hypoxemia. At 0.75 of gestation guinea pig dams were chronically catheterized. Control groups were exposed to room air, whereas study groups were exposed to a hypoxic atmosphere (10% oxygen, 2% carbon dioxide, and 88% nitrogen). To measure total and regional cerebral glucose utilization during normoxemia and isocapnic hypoxemia, we injected i.v. 100 microCi of 2-[3H]deoxyglucose into the dams. Total and regional cerebral glucose utilization were determined from the steady-state clearance of 2-deoxyglucose between the maternal arterial plasma and the fetal brain, the glucose concentration in the maternal arterial plasma, and the "lumped constant." During isocapnic hypoxemia, total fetal cerebral glucose utilization was not significantly higher than that previously measured during normoxemia (8 +/- 0.8 versus 8 +/- 1.0 micromol/100 g/min). Furthermore, no redistribution of cerebral glucose utilization could be detected. We conclude that moderate isocapnic hypoxemia in the immature fetal brain does not lead to any significant increase or redistribution of glucose utilization or to any major lactate accumulation. This may be related to the low cerebral metabolic demands of brain tissue at this stage of development. Whether this is the main reason for the known resistance of the immature fetal brain toward ischemic neuronal cell damage remains to be established.

Animals↗
PubMed1996

Selegiline enhances NGF synthesis and protects central nervous system neurons from excitotoxic and ischemic damage.

It has been previously demonstrated that selegiline, an irreversible monoamine oxidase B (MAO-B) inhibitor, potentiates glial reaction to injury and possesses some 'trophic-like' activities which do not depend on the inhibition of MAO-B and which are probably associated with the induction of astrocyte-derived neurotrophic substances. Based on these findings, we tried to find out whether selegiline is able to modify the expression of nerve growth factor (NGF) and to protect central nervous system (CNS) neurons from excitotoxic and ischemic damage. Selegiline (10 pM-1 nM) induced NGF messenger RNA (mRNA) expression in cultured rat cortical astrocytes as determined by reverse transcription-polymerase chain reaction (RT-PCR) followed by a corresponding increase in NGF protein content measured by two-site NGF-enzyme-linked immunosorbent assay (ELISA) in astrocyte-conditioned medium. Additionally, exposure of hippocampal cultures containing neuronal and glial cells to this drug at the same concentrations enhanced significantly the content of NGF measured in the culture medium after 6 h of incubation. We hypothesize that selegiline could rescue hippocampal neurons from injury by induction of astrocyte-derived NGF in this cell culture system. To test this hypothesis, an excitotoxic damage was induced in the same type of cells by exposure to 0.5 mM L-glutamate for 1 h. Selegiline (10 pM-1 nM) present in the growth medium 6 h before until 18 h after induction of injury (the point of glutamate-toxicity measurement) protected hippocampal neurons from excitotoxic death. Furthermore, administered intraperitoneally (i.p.) (8 x 15 mg/kg per day) this drug enhanced the expression of NGF message in intact rat cerebral cortex and protected rat cortical tissue from ischemic insult due to permanent occlusion of the middle cerebral artery (MCA). The neuroprotective activity of selegiline (5 x 10 mg/kg per day i.p.) was also demonstrated in a mouse model of focal cerebral ischemia. The present data show that selegiline induced NGF expression in cultured rat cortical astrocytes. In mixed primary cultures of hippocampal neuronal and glial cells, selegiline increased NGF protein content and protected hippocampal neurons from excitotoxic degeneration. In vivo, this drug induced NGF gene expression in cerebral cortex from intact rats and protected rat and mouse cortical tissue from ischemic insult after occlusion of the MCA. Our results indicate that the induction of astrocyte-derived NGF could contribute to the neuroprotective activity of selegiline demonstrated both in vivo and in vitro and can explain, in part, the 'trophic-like' properties of this compound which has been observed by others.

Animals↗
PubMed1996

Determination of intracellular Ca2+ concentration can be a useful tool to predict neuronal damage and neuroprotective properties of drugs.

The purpose of the present study was to examine the relationship between elevation in intracellular Ca2+ concentration ([Ca2+]i) and development of neuronal damage after cytotoxic hypoxia in vitro. Chick telencephalic neurons were exposed to NaCN 1 mM for up to 2 h. [Ca2+]i was assessed by means of fura-2 based microfluorometry and viability was measured by means of trypan blue exclusion on the same relocated cells for a period 24 h after initiation of hypoxia. Exposure to sodium cyanide resulted in an up to 10 fold increase in [Ca2+]i and led to subsequent neuronal damage. According to [Ca2+]i and viability neurons in four different stages could be revealed. The percentage of neurons showing elevated [Ca2+]i paralleled exactly the percentage of neuronal damage. The elevation in [Ca2+]i clearly preceded neuronal damage suggesting a time window for pharmacological intervention. The NMDA antagonists dizocilpine, memantine and amantadine were capable of reducing the percentage of neurons showing elevated [Ca2+]i and attenuated neuronal damage. Dizocilpine proved to be the most potent and amantadine to be the weakest antagonist whereas the alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionate (AMPA) antagonist 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo-(F)-quinoxaline (NBQX) was ineffective. Under our experimental conditions, measurement of [Ca2+]i was able to predict the extent of neuronal damage as well as the neuroprotective potency of drugs.

Amantadine↗
PubMed1996

Clenbuterol protects mouse cerebral cortex and rat hippocampus from ischemic damage and attenuates glutamate neurotoxicity in cultured hippocampal neurons by induction of NGF.

It has been shown previously that clenbuterol, a beta 2-adrenergic receptor agonist, enhances NGF synthesis in adult rat brain. Since NGF is able to protect neurons against damage, we tried to find out whether clenbuterol can rescue cultured hippocampal neurons from excitotoxic damage by induction of NGF. The neuroprotective activity of clenbuterol on neurons in the vulnerable CA1 subfield of the hippocampus was tested in a rat model of transient forebrain ischemia. Additionally, in the mouse model of focal cerebral ischemia the ability of clenbuterol to reduce the infarct size was examined. Exposure of mixed neuronal/glial hippocampal cultures to clenbuterol (1 to 100 microM) enhanced significantly the content of NGF measured in the culture medium by two-site ELISA. The excitotoxic injury was induced in the same type of cells after 14 days in vitro by exposure to 1 mM L-glutamate for 1 h in serum-free medium. NGF itself (0.15 to 100 ng/ml) added to the growth medium 4 h before until 18 h after induction of injury (the point of glutamate-toxicity measurement), protected hippocampal neurons from excitotoxic damage. Clenbuterol (1 to 100 microM) provided similar neuroprotection as NGF under the same experimental conditions. The neuroprotective activity of clenbuterol (100 microM) against glutamate-induced damage in hippocampal cultures was blocked by anti-NGF monoclonal antibodies (0.5 microgram/ml) added to the medium during the clenbuterol exposure, demonstrating that the neuronal rescue is mediated by NGF. Propranolol, a beta-adrenergic receptor antagonist (10 microM) added 20 min before and kept in the medium during exposure of the cultures to clenbuterol (1 microM) reversed the neuroprotective activity, suggesting that the induction of NGF and neuroprotection caused by clenbuterol are mediated via beta-adrenergic receptor activation. The capacity of clenbuterol to protect hippocampal neurons was also demonstrated in vivo in a rat model of transient forebrain ischemia. Clenbuterol (4 x 1 mg/kg) administered intraperitoneally increased the number of viable neurons in CA1 subfield of the rat hippocampus. Furthermore, clenbuterol (0.3 and 1 mg/kg, i.p. and 1 mg/kg, s.c.) reduced significantly the infarct area on the mouse brain surface after occlusion of the middle cerebral artery. The present data demonstrate that clenbuterol induces NGF synthesis in cultured hippocampal cells and protects hippocampal neurons from excitotoxic damage. The neuroprotective activity of clenbuterol is also demonstrated in vivo in two rodent models of cerebral ischemia. The results offer strong evidence that the neuroprotective activity of clenbuterol is caused by activation of beta-adrenergic receptors and the subsequent increased expression of NGF.

Animals↗
PubMed1996

Neuroprotective effects of alpha-lipoic acid and its enantiomers demonstrated in rodent models of focal cerebral ischemia.

The purpose of this study was to investigate whether alpha-lipoic acid (LA), the oxidized form of the radical scavenger dihydrolipoic acid (DLA), protected brain tissue against ischemic damage and whether there were differences in the neuroprotective potencies between its enantiomers. We used the models of focal cerebral ischemia in mice and rats. The infarct area on the mouse brain surface and the infarct volume of the rat brain were determined by means of an image analyzing system. The LA was capable of reducing the infarct area only when it was administered subcutaneously, but not when it was administered intraperitoneally or into the cisterna magna. Both the R- and the S-enantiomer of LA protected brain tissue against ischemic damage, but their protective activities seemed to be related to the time period of pretreatment. In mice, both enantiomers revealed a similar neuroprotective potency when they were administered subcutaneously 1 or 2 hr before occlusion of the middle cerebral artery (MCA), whereas a longer time period of pretreatment (4 or 6 hr) failed to exert neuroprotection. In rats, subcutaneous pretreatment with R- or S-LA for 2 hr before ischemia significantly diminished the infarct volume. We assume that LA has to be reduced to DLA which finally causes neuroprotection.

Animals↗
PubMed1996

Local cerebral glucose utilization in fetal guinea pigs at 0.75 gestation.

OBJECTIVE: Using the 2-deoxyglucose method, measurements of local cerebral glucose utilization in large fetal animals are very difficult and expensive. To circumvent these problems we recently modified the 2-deoxyglucose method for use in the fetal guinea pig in utero (Berger et al., J Neurochem 1994; 63: 271-279). The present study was designed to measure the rates of local cerebral glucose utilization in fetal guinea pigs at 0.75 of gestation. STUDY DESIGN: After intravenous injection of 14C 2-deoxyglucose into the dams, local cerebral glucose utilization of the fetuses was measured from the time integral of the tracer in the maternal plasma and the autoradiographically determined concentration of the tracer in various parts of the fetal brain. RESULTS: Fetal cerebral glucose utilization was low as compared to adult animals and varied in different brain structures from 19 +/- 4 to 29 +/- 7 mumol/100 g/min. CONCLUSION: This study demonstrates the feasibility to measure local cerebral glucose utilization in undisturbed fetal guinea pigs in utero. We conclude that the low rate of cerebral glucose utilization and its small overall variability may reflect the neurological immaturity of the fetal brain.

Animals↗
PubMed1996

Apparent independent action of nimodipine and glutamate antagonists to protect cultured neurons against glutamate-induced damage.

A disturbed cellular calcium homeostasis is suggested to play a pivotal role in neuronal damage. Energy deficiency causes depolarization of the neuronal membrane and Ca2+ enters the cells through different ion channels, the voltage-sensitive L-type Ca2+ channels and the NMDA-operated channels being the main gates. In the present study we used primary cultures of rat hippocampal neurons to demonstrate that the dihydropyridine calcium antagonist nimodipine, the non-competitive NMDA antagonists dizocilpine and memantine, as well as the AMPA antagonist NBQX (2,3-dihydroxy-6-nitro -7-sulfamoyl-benzo(F)quinoxaline), attenuate the glutamate-induced neuronal damage dose-dependently. Nimodipine applied simultaneously with NMDA-antagonists and NBQX, respectively, resulted in somewhat greater neuroprotection of glutamate-treated neurons compared with the effects of these agents applied singly. The type of interaction is best described by an independent action in combination, which means that the relative effects of nimodipine were not enhanced. Therefore, it can be considered as a lack of potentiation.

Animals↗
PubMed1996

TGF-beta 1 protects hippocampal neurons against degeneration caused by transient global ischemia. Dose-response relationship and potential neuroprotective mechanisms.

BACKGROUND AND PURPOSE: Transforming growth factor-beta 1 (TGF-beta 1) has been shown to rescue cultured neurons from excitotoxic and hypoxic cell death and to reduce infarct size after focal cerebral ischemia in mice and rabbits. The present study investigated the effects of TGF-beta 1 in a different pathophysiological setting and the delayed neuronal death of hippocampal pyramidal cells after transient global ischemia in rats, and evaluated the potential mechanisms of the neuroprotective activity of TGF-beta 1. METHODS: Transient forebrain ischemia was induced in male adult Wistar rats with bilateral occlusion of both common carotid arteries combined with systemic hypotension for 10 minutes. Seven days after ischemia, brains were perfusion-fixed and stained for histological evaluation. TGF-beta 1 or vehicle was injected intracerebroventricularly (ICV; 0.5, 4, and 50 ng) or intrahippocampally (4 ng) 1 hour before ischemia. For in vitro studies, hippocampal neurons were derived from E17 rat embryos and cultured for 10 to 14 days. Cells were exposed to (1) S-nitrosocysteine (SNOC; 30 mumol/L) to induce nitric oxide-induced oxidative injury and (2) staurosporine (0.03 mumol/L) to induce apoptotic cell death. RESULTS: Transient forebrain ischemia caused extensive degeneration of CA1 hippocampal pyramidal cells in vehicle-treated control animals. Ischemic injury was not significantly reduced after ICV administration of 0.5 ng TGF-beta 1 (71 +/- 7% damaged neurons versus 84 +/- 3% in vehicle-treated controls: n = 9 and 11, respectively; P = .07, Mann-Whitney U test). Administration of 4 ng TGF-beta 1 reduced the percentage of damaged CA1 pyramidal cells from 71 +/- 10% in controls to 52 +/- 7% in TGF-beta 1-treated animals (n = 11 and 12, respectively; P = .04). TGF-beta 1 (4 ng) also produced significant protection when injected directly into the hippocampal tissue. In contrast, ICV administration of 50 ng TGF-beta 1 failed to show a protective effect in two separate sets of experiments. In vitro, a 24-hour pretreatment of the cultured hippocampal neurons with TGF-beta 1 (0.1 to 10 ng/mL) significantly inhibited both nitric oxide and staurosporine neurotoxicity. Posttreatment with TGF-beta 1 (10 ng/mL) also inhibited staurosporine neurotoxicity but actually potentiated nitric oxide-induced neuronal injury. CONCLUSIONS: We demonstrated that TGF-beta 1 in a surprisingly low dose range has the capacity to reduce injury to CA1 hippocampal neurons caused by transient global ischemia in rats. This protective action could well be associated with the antioxidative and antiapoptotic effects of TGF-beta 1 demonstrated in vitro.

Animals↗
PubMed1995

Flupirtine protects neurons against excitotoxic or ischemic damage and inhibits the increase in cytosolic Ca2+ concentration.

We tested the effect of flupirtine against ischemic and excitotoxic neuronal damage as well as on the glutamate-induced rise in cytosolic calcium ion concentration (= [Ca2+]i). For in vivo experiments we used a model of focal cerebral ischemia in mice. The middle cerebral artery was permanently occluded and 48 h afterwards brain tissue was stained with neutral red, perfusion-fixed and the infarct surface was determined planimetrically. Pretreatment with flupirtine significantly reduced the infarct area (controls: 24.3 +/- 4.8 mm2, 1 mg/kg flupirtine: 20.1 +/- 3.6 mm2 and 10 mg/kg flupirtine: 19.5 +/- 3.9 mm2; P < 0.05), whereas postischemic application of flupirtine failed to reduce the infarct area. For in vitro studies, primary neuronal cultures were prepared from the hippocampi of newborn rats and excitotoxic damage was induced by exposing the cells to 500 mu M L-glutamate for 30 min. We could demonstrate that flupirtine (1-10 microM) was capable of protecting neurons against glutamate-induced cytotoxicity. In order to elucidate the underlying mechanism of action, we tested the effect of flupirtine on the glutamate-induced rise in [Ca2+]i using the Ca2+-indicator fura-2. L-Glutamate added in a final concentration of 100 microM to the cultured cells for 16 s caused a rise in [Ca2+]i from about 100 nM to 900 nM. Flupirtine (0.1-10 microM) reduced the glutamate-induced rise in [Ca2+]i concentration dependently.

Aminopyridines↗
PubMed1995

Tumor necrosis factors alpha and beta protect neurons against amyloid beta-peptide toxicity: evidence for involvement of a kappa B-binding factor and attenuation of peroxide and Ca2+ accumulation.

In Alzheimer disease (AD) the amyloid beta-peptide (A beta) accumulates in plaques in the brain. A beta can be neurotoxic by a mechanism involving induction of reactive oxygen species (ROS) and elevation of intracellular free calcium levels ([Ca2+]i). In light of evidence for an inflammatory response in the brain in AD and reports of increased levels of tumor necrosis factor (TNF) in AD brain we tested the hypothesis that TNFs affect neuronal vulnerability to A beta. A beta-(25-35) and A beta-(1-40) induced neuronal degeneration in a concentration- and time-dependent manner. Pretreatment of cultures for 24 hr with TNF-beta or TNF-alpha resulted in significant attenuation of A beta-induced neuronal degeneration. Accumulation of peroxides induced in neurons by A beta was significantly attenuated in TNF-pretreated cultures, and TNFs protected neurons against iron toxicity, suggesting that TNFs induce antioxidant pathways. The [Ca2+]i response to glutamate (quantified by fura-2 imaging) was markedly potentiated in neurons exposed to A beta, and this action of A beta was suppressed in cultures pretreated with TNFs. Electrophoretic mobility-shift assays demonstrated an induction of a kappa beta-binding activity in hippocampal cells exposed to TNFs. Exposure of cultures to I kappa B (MAD3) antisense oligonucleotides, a manipulation designed to induce NF-kappa B, mimicked the protection by TNFs. These data suggest that TNFs protect hippocampal neurons against A beta toxicity by suppressing accumulation of ROS and Ca2+ and that kappa B-dependent transcription is sufficient to mediate these effects. A modulatory role for TNF in the neurodegenerative process in AD is proposed.

Amyloid beta-Peptides↗
PubMed1995

Inhibitors of lipid peroxidation protect cultured neurons against cyanide-induced injury.

We tested the 21-aminosteroid U-74500A and the 2-methylaminochroman U-83836E, two potent inhibitors of lipid peroxidation, for their protective efficacy against cyanide- or Fe2+/Fe(3+)-induced damage of cultured neurons from chick embryo telencephalon. U-74500A (0.1-10 microM) as well as U-83836E (0.01-10 microM) reduced cyanide-induced neurotoxicity, indicating that lipid peroxidation plays an important role in the genesis of cyanide-induced neuronal injury. Both U-74500A and U-83836E, but not the NMDA antagonist dizocilpine (1 microM, prevented Fe2+/Fe(3+)-induced neuronal degeneration.

Animals↗
PubMed1995

Are NMDA or AMPA/kainate receptor antagonists more efficacious in the delayed treatment of excitotoxic neuronal injury?

At which time-point and to what extent do N-methyl-D-aspartate (NMDA) receptors, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)/kainate receptors and L-type voltage-sensitive Ca2+ channels (VSCC) contribute to glutamate-induced neuronal injury? To address this question, we induced glutamate neurotoxicity in two neuronal culture systems, chick telencephalic neurons and rat hippocampal neurons, and tested selective antagonists for their neuroprotective activity when administered either during the excitotoxic insult (acute treatment) or during the recovery period (posttreatment). In cultured chick telencephalic neurons exposed to 1 mM L-glutamate for 60 min, both the NMDA receptor antagonist dizocilpine (MK-801; 0.1 microM) and the AMPA/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 1 microM) completely blocked glutamate-induced neuronal injury when applied concomitantly with glutamate. If the antagonists were applied during the recovery period, dizocilpine at concentrations up to 10 microM only moderately increased cell viability, whereas CNQX showed a neuroprotective activity comparable to that observed in the case of the acute treatment. In cultured rat hippocampal neurons, excitotoxic injury was induced by a 30-min exposure to 1 microM glutamate. Treatment with dizocilpine during the glutamate exposure could rescue the hippocampal neurons from the excitotoxic insult, whereas acute treatment with the AMPA/kainate receptor antagonist 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo(F)-quinoxaline (NBQX) or the L-type VSCC blocker nimodipine showed no protection. In contrast, all three drugs showed neuroprotective activity when applied 30, 60 or 120 min after the glutamate exposure. Surprisingly, when the onset of the treatment was delayed for even 240 min, only NBQX and nimodipine led to a reduction in excitotoxic neuronal injury. We conclude that activation of AMPA/kainate receptors and L-type VSCC is critically involved in a late stage of glutamate neurotoxicity, thereby allowing pharmacological intervention at a time when blockade of NMDA receptors becomes less efficacious.

Animals↗
PubMed1995

Prolonged pretreatment with alpha-lipoic acid protects cultured neurons against hypoxic, glutamate-, or iron-induced injury.

The antioxidant dihydrolipoic acid has been shown to reduce hypoxic and excitotoxic neuronal damage in vitro. In the present study, we tested whether pretreatment with alpha-lipoic acid, which presumably allows endogenous formation of dihydrolipoic acid, can protect cultured neurons against injury caused by cyanide, glutamate, or iron ions, using the trypan blue exclusion method to determine neuronal damage. One hour of preincubation with dihydrolipoic acid (1 microM), but not with alpha-lipoic acid, reduced damage of neurons from chick embryo telencephalon caused by 1 mM sodium cyanide or iron ions. alpha-Lipoic acid (1 microM) reduced cyanide-induced neuronal damage when added 24 h before hypoxia, and pretreatment with alpha-lipoic acid for > 24 h enhanced this neuroprotective effect. Both the R- and the S-enantiomer of alpha-lipoic acid exerted a similar neuroprotective effect. Pretreatment with alpha-lipoic acid (1 microM) from the day of plating onward prevented the degeneration of chick embryo telencephalic neurons that had been exposed to Fe2+/Fe3+. alpha-Lipoic acid (1 microM) added to the culture medium the day of plating also reduced neuronal injury induced by 1 mM L-glutamate in rat hippocampal cultures, whereas 30 min of preincubation with alpha-lipoic acid failed to attenuate glutamate-induced neuronal damage. Our results indicate that neuroprotection by prolonged pretreatment with alpha-lipoic acid is probably due to the radical scavenger properties of endogenously formed dihydrolipoic acid.

Animals↗