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J B Schulz

Publications and source records attributed to J B Schulz.

At least 37 records · Page 2Linked to original sources
PubMed2001

Sensitivity to MPTP is not increased in Parkinson's disease-associated mutant alpha-synuclein transgenic mice.

Environmental and genetic factors that contribute to the pathogenesis of Parkinson's disease are discussed. Mutations in the alpha-synuclein (alphaSYN ) gene are associated with rare cases of autosomal-dominant Parkinson's disease. We have analysed the dopaminergic system in transgenic mouse lines that expressed mutant [A30P]alphaSYN under the control of a neurone-specific Thy-1 or a tyrosine hydroxylase (TH) promoter. The latter mice showed somal and neuritic accumulation of transgenic [A30P]alphaSYN in TH-positive neurones in the substantia nigra. However, there was no difference in the number of TH-positive neurones in the substantia nigra and the concentrations of catecholamines in the striatum between these transgenic mice and non-transgenic littermates. To investigate whether forced expression of [A30P]alphaSYN increased the sensitivity to putative environmental factors we subjected transgenic mice to a chronic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) regimen. The MPTP-induced decrease in the number of TH-positive neurones in the substantia nigra and the concentrations of catecholamines in the striatum did not differ in any of the [A30P]alphaSYN transgenic mouse lines compared with wild-type controls. These results suggest that mutations and forced expression of alphaSYN are not likely to increase the susceptibility to environmental toxins in vivo.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2001

Dopamine mediates striatal malonate toxicity via dopamine transporter-dependent generation of reactive oxygen species and D2 but not D1 receptor activation.

Intrastriatal injection of the reversible succinate dehydrogenase inhibitor malonate results in both chemically induced hypoxia and striatal lesions that are similar to those seen in Huntington's disease and cerebral ischaemia. The mechanisms leading to neuronal death involve secondary excitotoxicity, the release of dopamine from nigrostriatal fibres and the generation of reactive oxygen species (ROS) including nitric oxide (NO) and hydroxyl radicals. Here, we further investigated the contribution and mechanism of dopamine on malonate-induced striatal lesions. Prior lesions of the nigrostriatal pathway with 6-OHDA or the depletion of striatal dopamine stores by pretreatment with reserpine, an inhibitor or the vesicular monoamine transporter type-2 (VMAT2), in combination with alpha-methyl-p-tyrosine resulted in a significant reduction of malonate-induced striatal lesion volumes. This was paralleled by block or reduction of the malonate-induced generation of ROS, as measured by the conversions of salicylate to 2,3-dihydroxybenzoic acid (2,3-DHBA) using microdialysis. Systemic or intrastriatal application of L-DOPA or dopamine, respectively, reconstituted malonate toxicity and the generation of ROS in 6-OHDA-lesioned rats. Block of the dopamine transporter by GBR12909 did not result in a reduction of malonate-induced dopamine release, but significantly reduced the generation of hydroxyl radicals. The D2 receptor agonist lisuride and the mixed D1 and D2 receptor agonist apomorphine, but not the D1 receptor agonist SKF38393, partially restored malonate toxicity in 6-OHDA-lesioned rats without increasing the generation of ROS. In line with these results sulpiride, an inhibitor of D2 receptors, reduced the malonate-induced lesion volume, whereas SCH23390, an inhbitor of D1 receptors, was ineffective. Our data suggest that malonate-induced dopamine toxicity to energetically impaired neurons is mediated by two independent pathways: (i) dopamine transporter uptake-dependent, dopamine receptor-independent generation of ROS, and (ii) excessive stimulation of D2 receptors.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2001

Rescue from death but not from functional impairment: caspase inhibition protects dopaminergic cells against 6-hydroxydopamine-induced apoptosis but not against the loss of their terminals.

Despite the identification of several mutations in familial Parkinson's disease (PD), the underlying mechanisms of dopaminergic neuronal loss in idiopathic PD are still unknown. To study whether caspase-dependent apoptosis may play a role in the pathogenesis of PD, we examined 6-hydroxydopamine (6-OHDA) toxicity in dopaminergic SH-SY5Y cells and in embryonic dopaminergic mesencephalic cultures. 6-OHDA induced activation of caspases 3, 6 and 9, chromatin condensation and cell death in SH-SY5Y cells. The caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-(O-methyl)fluoromethylketone (zVAD-fmk) or adenovirally mediated ectopic expression of the X-chromosomal inhibitor of apoptosis protein (XIAP) blocked caspase activation and prevented death of SH-SY5Y cells. Similarly, zVAD-fmk provided protection from 6-OHDA-induced loss of tyrosine hydroxylase-positive neurones in mesencephalic cultures. In contrast, zVAD-fmk failed to protect mesencephalic dopaminergic neurones from 6-OHDA-induced loss of neurites and reduction of [(3)H]dopamine uptake. These data suggest that, although caspase inhibition provides protection from 6-OHDA-induced death of dopaminergic neurones, the neurones may remain functionally impaired.

Adenoviridae↗
PubMed2000

Protection by synergistic effects of adenovirus-mediated X-chromosome-linked inhibitor of apoptosis and glial cell line-derived neurotrophic factor gene transfer in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine model of Parkinson's disease.

1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) produces clinical, biochemical, and neuropathological changes reminiscent of those occurring in idiopathic Parkinson's disease (PD). Here we show that a peptide caspase inhibitor, N-benzyloxy-carbonyl-val-ala-asp-fluoromethyl ketone, or adenoviral gene transfer (AdV) of a protein caspase inhibitor, X-chromosome-linked inhibitor of apoptosis (XIAP), prevent cell death of dopaminergic substantia nigra pars compacta (SNpc) neurons induced by MPTP or its active metabolite 1-methyl-4-phenylpyridinium in vitro and in vivo. Because the MPTP-induced decrease in striatal concentrations of dopamine and its metabolites does not differ between AdV-XIAP- and control vector-treated mice, this protection is not associated with a preservation of nigrostriatal terminals. In contrast, the combination of adenoviral gene transfer of XIAP and of the glial cell line-derived neurotrophic factor to the striatum provides synergistic effects, rescuing dopaminergic SNpc neurons from cell death and maintaining their nigrostriatal terminals. These data suggest that a combination of a caspase inhibitor, which blocks death, and a neurotrophic factor, which promotes the specific function of the rescued neurons, may be a promising strategy for the treatment of PD.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2000

Oxidative stress in patients with Friedreich ataxia.

Increased generation of reactive oxygen species may underlie the pathophysiology of Friedreich ataxia (FRDA). The authors measured concentrations of 8-hydroxy-2'-deoxyguanosine (8OH2'dG), a marker of oxidative DNA damage, in urine and of dihydroxybenzoic acid (DHBA), a marker of hydroxyl radical attack, in plasma of 33 patients with FRDA. They found a 2.6-fold increase in normalized urinary 8OH2'dG but no change in plasma DHBA as compared with controls. Oral treatment with 5 mg/kg/day of the antioxidant idebenone for 8 weeks significantly decreased urinary 8OH2'dG concentrations, indicating that 8OH2'dG may be useful in monitoring therapeutic interventions in patients with FRDA.-1721

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2000

Flupirtine and retigabine prevent L-glutamate toxicity in rat pheochromocytoma PC 12 cells.

Flupirtine is an analgesic drug thought to have NMDA receptor antagonistic and antiapoptotic effects. We investigated the effects of Ethyl-2-amino-6-(4-(4-fluorbenzyl)amino)-pyridine-3-carbamamic+ ++ acid, maleate (flupirtine) and the related compound N-(2-amino-4-(4-fluorobenzylamino)-phenyl)-carbamic acid, ethyl ester) (retigabine) (Desaza-flupirtine) on the toxicity of L-glutamate and L-3,4-dihydroxyphenylalanine (L-DOPA) in rat pheochromocytoma PC 12 cells in vitro. Both drugs (10 microM) markedly decreased nonreceptor-mediated necrotic cell death in PC 12 cultures treated with L-glutamate (10 mM) for 72 h. In contrast, apoptosis induced by L-DOPA (250 microM) after 48 h was not affected by either substance. While L-DOPA elicited massive generation of reactive oxygen intermediates, L-glutamate-induced cell death was accompanied by only slightly increased levels of reactive oxygen intermediates. Flupirtine and retigabine exerted anti-oxidative effects in PC 12 cultures independent of their ability to prevent cell death. Further examination of the protective action of flupirtine and retigabine against L-glutamate toxicity showed that it had no influence on monoamine oxidase (monoamine: oxygen oxidoreductase (deaminating), EC 1.4.3.4., MAO) activity. Thus, flupirtine and retigabine provided protection against cystine deprivation and L-glutamate toxicity but did not protect against L-glutamate under cystine-free conditions indicating that both compounds are sufficiently effective to compensate the oxidative stress elicited by cystine deprivation but not excessive activity of monoamine oxidase after L-glutamate treatment.

Aminopyridines↗
PubMed2000

Insulin-like growth factor-1-mediated protection from neuronal apoptosis is linked to phosphorylation of the pro-apoptotic protein BAD but not to inhibition of cytochrome c translocation in rat cerebellar neurons.

Cerebellar granule neurons cultured in the presence of serum and depolarizing potassium concentrations undergo apoptosis when switched to serum-free medium containing physiological potassium concentrations but remain viable after serum deprivation alone. Here, we show that potassium deprivation is associated with the dephosphorylation of the BCL-2-related BAD protein. Exposure to insulin-like growth factor-1 (IGF-1) inhibits both apoptosis and dephosphorylation of BAD. Both effects of IGF-1 do not depend on protein synthesis but are nullified by the phosphatidylinositol-3 kinase inhibitors, wortmannin and LY294002. In contrast to the treatment with cycloheximde, IGF-1 does not block the translocation of cytochrome c from mitochondria to the cytosol. Further, dephosphorylation of BAD alone does not appear to be sufficient to trigger apoptosis, since inhibition of protein synthesis by cycloheximide prevents apoptosis, but not BAD dephosphorylation, after potassium deprivation. These results suggest the coexistence of two parallel pathways, protein synthesis-dependent cytochrome c translocation and protein synthesis-independent dephosphorylation of BAD, both of which have to be activated to induce neuronal apoptosis.

Androstadienes↗
PubMed2000

Altered expression of calcium- and apoptosis-regulating proteins in multiple system atrophy Purkinje cells.

The expression patterns of the calcium binding proteins calbindin and parvalbumin and of the apoptosis modulating proteins Bcl-2, Bax, and Bcl-x were studied in the cerebellum of patients with multiple system atrophy (MSA). Calbindin and parvalbumin immunoreactivity was markedly decreased in MSA Purkinje cells whereas Bax and Bcl-x protein expression was increased. Bcl-2 expression was restricted to a subpopulation of granule neurons, but no decrease of Bcl-2 was evident in MSA. Additional DNA end-labeling (ISEL) studies revealed only one possible apoptotic Purkinje cell nucleus, but nuclei in the cerebellar white matter, probably oligodendrocytes, in the cerebellum of patients with MSA. The present results suggest that a diminished calcium binding capacity of MSA Purkinje cells might lead to a change in the regulation of proteins of the bcl-2 family that could favor the pathologic initiation of apoptosis.

Apoptosis↗
PubMed2000

Effect of 1-methyl-4-phenylpyridinium on glutathione in rat pheochromocytoma PC 12 cells.

We investigated the effect of the selective dopaminergic neurotoxin 1-methyl-4-phenylpyridinium (MPP+) on glutathione redox status and the generation of reactive oxygen intermediates (ROI) in rat pheochromocytoma PC 12 cells in vitro. Treatment with MPP+ (250 microM) led to a 63% increase of reduced glutathione (GSH) after 24 h, while a 10-fold higher concentration of MPP+ (2.5 mM) depleted cellular GSH to 12.5% of control levels within that time. Similarly, the complex I-inhibitor rotenone induced a time-dependent loss of GSH at 1 and 10 microM, whereas treatment with lower concentrations of rotenone (0.1, 0.01 microM) increased cellular GSH. Both MPP+ and rotenone increased cellular levels of oxidised glutathione (GSSG) and the higher concentrations of both compounds led to an elevated ratio of oxidised glutathione (GSSG) vs total glutathione (GSH + GSSG) indicating a shift in cellular redox balance. MPP+ or rotenone did not induce the generation of ROI or significant elevation of intracellular levels of thiobabituric acid reactive substances (TBARS) for up to 48 h. Our data suggest that MPP+ has differential effects on glutathione homeostasis depending on the degree of complex I-inhibition and that inhibition of complex I is not sufficient to generate ROI in this paradigm.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2000

Evoked potentials in multiple system atrophy (MSA).

OBJECTIVES: To study the involvement of pyramidal tracts and sensory pathways in multiple system atrophy (MSA). MATERIALS AND METHODS: Evoked potential studies were performed in 45 MSA patients suffering from either MSA of cerebellar type (MSA-C) or MSA of parkinsonian type (MSA-P). RESULTS: Motor evoked potentials were normal in all MSA patients, whereas visual and somatosensory evoked potential abnormalities were found in about 40% of the MSA patients with no significant difference between the cerebellar (MSA-C) and parkinsonian (MSA-P) subgroup. Abnormal latencies of wave III in brainstem auditory evoked potentials were significantly more frequent in MSA-C. CONCLUSIONS: Abnormalities of somatosensory, visual and auditory evoked potentials are frequent findings in MSA, whereas abnormal motor evoked potentials are not a characteristic feature of the disease.

Adult↗
PubMed2000

Glutathione, oxidative stress and neurodegeneration.

There is significant evidence that the pathogenesis of several neurodegenerative diseases, including Parkinson's disease, Alzheimer's disease, Friedreich's ataxia and amyotrophic lateral sclerosis, may involve the generation of reactive oxygen species and mitochondrial dysfunction. Here, we review the evidence for a disturbance of glutathione homeostasis that may either lead to or result from oxidative stress in neurodegenerative disorders. Glutathione is an important intracellular antioxidant that protects against a variety of different antioxidant species. An important role for glutathione was proposed for the pathogenesis of Parkinson's disease, because a decrease in total glutathione concentrations in the substantia nigra has been observed in preclinical stages, at a time at which other biochemical changes are not yet detectable. Because glutathione does not cross the blood-brain barrier other treatment options to increase brain concentrations of glutathione including glutathione analogs, mimetics or precursors are discussed.

Alzheimer Disease↗
PubMed2000

Deficiency of inducible nitric oxide synthase protects against MPTP toxicity in vivo.

MPTP produces clinical, biochemical, and neuropathologic changes reminiscent of those that occur in idiopathic Parkinson's disease (PD). In the present study we show that MPTP treatment led to activation of microglia in the substantia nigra pars compacta (SNpc), which was associated and colocalized with an increase in inducible nitric oxide synthase (iNOS) expression. In iNOS-deficient mice the increase of iNOS expression but not the activation of microglia was blocked. Dopaminergic SNpc neurons of iNOS-deficient mice were almost completely protected from MPTP toxicity in a chronic paradigm of MPTP toxicity. Because the MPTP-induced decrease in striatal concentrations of dopamine and its metabolites did not differ between iNOS-deficient mice and their wild-type littermates, this protection was not associated with a preservation of nigrostriatal terminals. Our results suggest that iNOS-derived nitric oxide produced in microglia plays an important role in the death of dopaminergic neurons but that other mechanisms contribute to the loss of dopaminergic terminals in MPTP neurotoxicity. We conclude that inhibition of iNOS may be a promising target for the treatment of PD.

Animals↗
PubMed2000

Neuroprotection by the inhibition of apoptosis.

Accumulating evidence strongly suggests that apoptosis contributes to neuronal cell death in a variety of neurodegenerative contexts. Activation of the cysteine protease caspase-3 appears to be a key event in the execution of apoptosis in the central nervous system (CNS). As a result, mice null for caspase-3 display considerable neuronal expansion usually resulting in death by the second week of life. At present, 14 caspase family members have been identified and subdivided into three subgroups on the basis of preference for specific tetrapeptide motifs using a positional scanning combinatorial substrate library. Caspase-3 is a group II member (2, 3, 7) categorized by an absolute substrate requirement for aspartic acid in the P4 position of the scissile bond. The preferred cleavage motif (DExD) for group II caspases is found in many structural, metabolic and repair proteins essential for cellular homeostasis. Consistent with the proposal that apoptosis plays a central in role human neurodegenerative disease, caspase-3 activation has recently been observed in stroke, spinal cord trauma, head injury and Alzheimer's disease. Indeed, peptide-based caspase inhibitors prevent neuronal loss in animal models of head injury and stroke suggesting that these compounds may be the forerunners of non-peptide small molecules that halt apoptosis processes implicated in these neurodegenerative disorders. A clear link between an hereditary neurodegenerative disorder and failed caspase inhibition has recently been proposed for spinal muscular atrophy (SMA). In severe SMA, the neuronal specific inhibitor of apoptosis (IAP) family member known as NAIP is often dysfunctional due to missense and truncation mutations. IAPs such as NAIP potently block the enzymatic activity of group II caspases (3 and 7) suggesting that NAIP mutations may permit unopposed developmental apoptosis to occur in sensory and motor systems resulting in lethal muscular atrophy. Conversely, adenovirally-mediated overexpression of NAIP or the X-linked IAP called XIAP reduces the loss of CA1 hippocampal neurons following transient forebrain ischemia. Taken together, these findings suggest that anti-apoptotic strategies may some day have utility in the treatment of neurodegenerative disease. The present review will summarize some of the recent evidence suggesting that apoptosis inhibitors may become a practical therapeutic approach for both acute and chronic neurodegenerative conditions.

Animals↗
PubMed2000

Nerve conduction studies in multiple system atrophy.

To study the frequency and severity of peripheral neuropathy in multiple system atrophy (MSA), we performed nerve conduction studies in 42 MSA patients suffering from either cerebellar MSA (MSA-C) or parkinsonian MSA (MSA-P). Abnormal nerve conduction was present in 24% of the patients. Abnormalities were significantly more frequent in MSA-P (43%) compared to MSA-C (14%). Motor nerve conduction velocities were reduced in 4% of the MSA-C and in 7% of the MSA-P patients. Abnormal compound muscle action potentials were more frequent in MSA-P (29% versus 7% in MSA-C) pointing to a more pronounced loss of motor axons in this subgroup. Sensory nerve conduction velocities were abnormal in 4% of the MSA-C and 14% of the MSA-P patients, and mean sensory nerve action potentials were normal in all MSA-C and reduced in 7% of the MSA-P patients. The data provide evidence that the peripheral nervous system is differentially affected in MSA-C and MSA-P.

Action Potentials↗
PubMed1999

MPP+ inhibits proliferation of PC12 cells by a p21(WAF1/Cip1)-dependent pathway and induces cell death in cells lacking p21(WAF1/Cip1).

The molecular and biochemical mode of cell death of dopaminergic neurons in Parkinson's disease (PD) is uncertain. In an attempt at further clarification we studied the effects of 1-methyl-4-phenylpyridinium (MPP+), the active metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), on dopaminergic PC12 cells. In humans and nonhuman primates MPTP/MPP+ causes a syndrome closely resembling PD. MPP+ toxicity is thought to be mediated by the block of complex I of the mitochondrial electron transport chain. Treatment of undifferentiated PC12 cells with MPP+ primarily inhibited proliferation of PC12 cells and secondarily led to cell death after the depletion of all energy substrates by glycolysis. This cell death showed no morphological characteristics of apoptosis and was not blocked by treatment with caspase inhibitors. The inhibition of cell growth was not dependent on an inhibition of complex I activity since MPP+ also inhibited cell proliferation in SH-SY5Y cells lacking mitochondrial DNA and complex I activity (p0 cells). As shown by flow cytometric analysis, MPP+ induced a block in the G0/G1 to S phase transition that correlated with increased expression of the cyclin-dependent kinase inhibitor p21(WAF1/Cip1) and growth arrest. Since treatment with 1 microM MPP+ caused apoptotic cell death in p21(WAF1/Cip1)-deficient (p21(-/-)) but not in parental (p21(+/+)) mouse embryo fibroblasts, our data suggest that in an early phase MPP+-induced p21(WAF1/Cip1) expression leads to growth arrest and prevents apoptosis until energy depletion finally leads to a nonapoptotic cell death.

1-Methyl-4-phenylpyridinium↗
PubMed1999

Glutathione depletion and neuronal cell death: the role of reactive oxygen intermediates and mitochondrial function.

Glutathione (GSH) levels are supposed to determine the vulnerability of many cells towards a wide array of insults. We investigated the effects of chronic inhibition of GSH synthesis and acute depletion of GSH on cerebellar granule neurons in vitro and determined cytoplasmic and mitochondrial GSH with relation to mitochondrial function and generation of reactive oxygen intermediates (ROI). l-buthionine sulfoximine (BSO), which irreversibly blocks gamma-glutamyl-cysteine synthase, led to a time- and concentration-dependent loss of cytoplasmic GSH, while mitochondrial GSH was relatively preserved. No increased generation of ROI was detected over 48 h and the mitochondrial membrane potential was largely maintained. Neuronal degeneration occurred when mitochondrial GSH levels had fallen below 50% of control after 24-36 h. In contrast, direct conjugation of mitochondrial and cytoplasmic GSH with etacrynic acid (EA), resulted in immediate loss of mitochondrial GSH, a large increase of ROI within 2 h, subsequent collapse of the mitochondrial membrane potential and complete cell death within 4-8 h. Electron microscopy studies revealed an as yet unknown change of the chromatin structure to a homogeneous granular pattern after BSO, while EA resulted in typical necrotic changes. No typical features of apoptosis, i.e., no chromatin condensation or DNA fragmentation were detected after GSH depletion after BSO or EA treatment.

Animals↗
PubMed1999

Differential effects of L-buthionine sulfoximine and ethacrynic acid on glutathione levels and mitochondrial function in PC12 cells.

We investigated the effect of glutathione (GSH) depletion on mitochondrial function and generation of reactive oxygen intermediates (ROI) in PC12 cells in vitro. Direct depletion of cellular GSH using ethacrynic acid (EA, 500 mM) resulted in a concentration-dependent generation of ROI and cell death within 24 h. Treatment with 500 microM L-buthionine sulfoximine (BSO), which inhibits GSH synthesis, reduced cellular GSH but did not lead to generation of ROI. Furthermore, cells remained viable up to 72 h. Analysis of subcellular fractions revealed complete loss of cytosolic and mitochondrial GSH within 4 h of EA treatment. In contrast, BSO-treated cells still maintained 100% GSH in the mitochondrial fraction for 4 h and 6% for 48 h. Mitochondrial complex II/IIi and IV activities were not significantly decreased up to 48 h of BSO treatment while EA treatment resulted in a complete loss of complex II/III activity and a 70% reduction of complex IV activity within 4 h. These findings suggest that mitochondrial GSH is critical for the maintenance of mitochondrial function and cellular viability.

Animals↗