Alzheimer Disease: Bigl M

Joerchel S, Raap M, Bigl M, Eschrich K, Schliebs R. · Paul Flechsig Institute for Brain Research, University of Leipzig, Leipzig, Germany. · Int J Dev Neurosci. · Pubmed #18325718 No free full text.

Abstract: Alzheimer's disease (AD) is characterized by cholinergic dysfunction and progressive basal forebrain cell loss which has been hypothesized to be associated with extensive accumulation of beta-amyloid (Abeta). To reveal whether oligomeric Abeta displays a particular toxicity for cholinergic neurons, the cholinergic cell line SN56.B5.G4 (SN56) was used as a model. Recently performed microarray analyses demonstrated that genes affected by exposure of SN56 cells with 50 microM oligomeric Abeta(1-42) for 24 h were involved in protein modification and degradation [Heinitz, K., Beck, M., Schliebs, R., Perez-Polo, J.R., 2006. Toxicity mediated by soluble oligomers of beta-amyloid(1-42) on cholinergic SN56.B5.G4 cells. J. Neurochem. 98, 1930-1945]. Using a proteomic approach, we compared the levels of proteins and specially of phosphorylated proteins in cytosolic fractions of cell lysates from cholinergic SN56 cells exposed to 50 microM Abeta(1-42) for 24h to those in control incubations. We show here that the levels of calreticulin, and mitogen-activated protein kinase (MAPK) kinase 6c were up-regulated in cholinergic SN56 cells exposed to Abeta(1-42), while gamma-actin appeared down-regulated. Abeta(1-42) exposure of cholinergic SN56 cells led to decreased phosphorylation of phosphoproteins, such as the Rho GDP dissociation inhibitor, the ubiquitin carboxyl terminal hydrolase-1, and the tubulin alpha-chain isotype Malpha6, as compared to untreated control lysates. The proteins identified have also been reported to be affected in brains of AD patients, suggesting a potential role of Abeta in influencing the integrity and functioning of the proteome in AD.

Apelt J, Bigl M, Wunderlich P, Schliebs R. · Department of Neurochemistry, University of Leipzig, Paul Flechsig Institute for Brain Research, Jahnallee 59, D-04109 Leipzig, Germany. · Int J Dev Neurosci. · Pubmed #15465277 No free full text.

Abstract: The molecular mechanisms of beta-amyloidogenesis in sporadic Alzheimer's disease are still poorly understood. To reveal whether aging-associated increases in brain oxidative stress and inflammation may trigger onset or progression of beta-amyloid deposition, a transgenic mouse (Tg2576) that express the Swedish double mutation of human amyloid precursor protein (APP) was used as animal model to study the developmental pattern of markers of oxidative stress and APP processing. In Tg2576 mouse brain, cortical levels of soluble beta-amyloid (1-40) and (1-42) steadily increased with age, but significant deposition of fibrillary beta-amyloid in cortical areas did not occur before postnatal age of 10 months. The slope of increase in cerebral cortical beta-secretase (BACE1) activities in Tg2576 mice between ages of 9 and 13 months was significantly higher as compared to that of the alpha-secretase, while the expression level of BACE1 protein and mRNA did not change with age. The activities of superoxide dismutase and glutathione peroxidase in cortical tissue from Tg2576 mice steadily increased from postnatal age 9-12 months. The levels of cortical nitric oxide, and reactive nitrogen species demonstrated peak values around 9 months of age, while the level of interleukin-1beta steadily increased from postnatal month 13 onwards. The developmental temporal coincidence of increased levels of reactive nitrogen species and antioxidative enzymes with the onset of beta-amyloid plaque deposition provides further evidence that developmentally and aging-induced alterations in brain oxidative status exhibit a major factor in triggering enhanced production and deposition of beta-amyloid, and potentially predispose to Alzheimer's disease.

Blasko I, Beer R, Bigl M, Apelt J, Franz G, Rudzki D, Ransmayr G, Kampfl A, Schliebs R. · Department of Psychiatry, University Hospital of Innsbruck, Innsbruck, Austria. · J Neural Transm. · Pubmed #15057522 No free full text.

Abstract: Traumatic brain injury (TBI) is a risk factor for the development of Alzheimer's disease (AD). After a traumatic brain injury depositions of amyloid beta (Abeta) in the brain parenchyma were found. In this study we investigated the expression pattern of beta-secretase (BACE-1) in ipsi- or contralateral hippocampus and cortex following controlled cortical TBI in rats. BACE-1 mRNA levels, estimated by real time RT-PCR, were elevated 24 h post injury, and persisting up to 72 h, in the ipsi- and contralateral hippocampus and cerebral cortex as compared to the sham-treated animals (p<0.01). The TBI-induced changes in BACE-1 mRNA are due to enhanced hippocampal and cortical expression of BACE-1 mRNA in neurons and reactive astrocytes as revealed by in situ hybridization. The alterations in hippocampal BACE-1 mRNA levels are accompanied by corresponding increases in BACE-1 protein levels in ipsi- and contralateral hippocampus and ipsilateral cortex as demonstrated by Western blot analysis. In contrast, in the contralateral cortex only a weak increase of traumatically induced BACE-1 protein production was found. The activity of BACE-1 as measured by the formation of the cleavage product of amyloid beta precursor protein, transiently increased up to 48 h after injury, but returned to basal level 7 days post injury. This study demonstrates that the beta-secretase is stimulated following TBI and may suggest a mechanism for the temporal increase of Abeta levels observed in patients with brain trauma.

Bigl M, Apelt J, Eschrich K, Schliebs R. · Institute of Biochemistry, University of Leipzig, Leipzig, Germany. · J Neural Transm. · Pubmed #12541014 No free full text.

Abstract: Alzheimer's disease is associated with markedly impaired cerebral glucose metabolism as detected by reduced cortical desoxyglucose utilization, by altered activities of key glycolytic enzymes or by reduced densities of cortical glucose transporter subtypes. To determine whether formation and/or deposition of beta-amyloid plays a role in the pathology of glucose metabolism, transgenic Tg2576 mice that overexpress the Swedish mutation of the human amyloid precursor protein and demonstrate a progressive, age-related cortical and hippocampal deposition of beta-amyloid plaques, were used to study expression and activity of key enzymes of brain glycolysis (phosphofructokinase, PFK) and glyconeogenesis (fructose1,6-bisphosphatase; FbPase). Quantitative RT-PCR revealed high expression levels of both C- and M-type PFK mRNA in non-transgenic mouse cerebral cortex, whilst there was little expression of the L-type. In 24-month-old transgenic Tg2576 mouse cortex, but not in 7-, 13-, and 17-month-old mice, the copy number of PFK-C mRNA was significantly reduced in comparison to non-transgenic littermates, while the mRNA level of the other PFK isoforms and FbPase did not differ between transgenic and non-transgenic tissue samples. In situ hybridization in brain sections from aged Tg2576 mice revealed reduced PFK-C mRNA expression in beta-amyloid plaque-associated neurons and upregulation in reactive astrocytes surrounding beta-amyloid deposits. The decreased PFK-C protein level detected by Western analysis in cerebral cortical tissue from 24-month-old transgenic Tg2576 mice was accompanied by reduced enzyme activity of PFK in comparison to non-transgenic littermates. Our data demonstrate that impairment of cerebral cortical glucose metabolism occurs only due to the long-lasting high beta-amyloid burden. This results from a reduction in glycolytic activity in beta-amyloid plaque-associated neurons and a concomitant upregulation in reactive, plaque-surrounding astrocytes.

Krügel U, Bigl V, Eschrich K, Bigl M. · Rudolf Boehm Institute of Pharmacology and Toxicology, Medical Faculty, University of Leipzig, Härtelstrasse 16-18, D-04107, Leipzig, Germany. · Int J Dev Neurosci. · Pubmed #11337195 No free full text.

Abstract: Changes in the metabolic activity within the brain of patients suffering from Alzheimer's disease (AD) were investigated and compared with biochemical alterations in the hippocampus induced by fimbria/fornix transection in the rat. The deafferentation of the hippocampus results in a degeneration of cholinergic septo-hippocampal terminals accompanied by a persistent decrease of choline acetyltransferase (ChAT) and acetylcholine esterase (AChE) activities similar to the cholinergic malfunction in AD. In the animal model the [3H]-cytochalasin B binding to the glucose transporters was elevated up to the day 7 after surgery as was the activity of the phosphofructokinase (PFK) on day 3. A reactive astrogliosis could be evidenced by the upregulation of glial fibrillary acidic protein (GFAP). An increase of the PFK activity was also found in AD being accompanied by enhanced level of GFAP as well. A higher concentration of mRNA for all three isoenzymes of PFK was shown by reverse transcription (RT)-real time polymerase chain reaction (PCR) amplification. However, the pattern of PFK isoenzyme proteins and mRNAs did neither change in diseased human nor in the lesioned rat brain. The activities of the mitochondrial enzymes pyruvate dehydrogenase complex (PDHC) and cytochrome c oxidase (CO) were diminished in the lesioned rat hippocampus on day 7 as well as in AD brain. Subcellular fractionation showed that the activity of these enzymes was affected in the synaptosomal as well as in the extrasynaptosomal mitochondria indicating a loss of neuronal input and also a vulnerability of intrinsic hippocampal neurons and/or non-neuronal cells. The recovery of the mitochondrial enzyme activity in the animal model at later post lesion intervals may be the result of compensatory responses of surviving cells or of sprouting of other non-affected inputs. It is concluded that common metabolic mechanisms may underlie the concurrent degenerative and repair processes in the denervated hippocampus and the diseased Alzheimer brain.

Bigl M, Apelt J, Luschekina EA, Lange-Dohna C, Rossner S, Schliebs R. · Institute of Biochemistry, University of Leipzig, Liebigstrasse 16, D-04103 Leipzig, Germany. · Neurosci Lett. · Pubmed #10998560 No free full text.

Abstract: On the basis of the recent cloning of the beta-secretase, the beta-site amyloid precursor protein (APP)-cleaving enzyme (BACE), (Science, 286 (1999) 735), digoxigenin-labelled riboprobes were generated to localize the cellular expression pattern of BACE mRNA in brain sections of transgenic Tg2576 mice, overexpressing the Swedish mutation of the APP695 isoform. Non-radioactive in situ hybridization in combination with immunohistochemistry to identify the cell types and beta-amyloid deposits revealed strong BACE mRNA hybridization signals in neurons of the cerebral cortex, hippocampal formation, thalamus and cholinergic basal forebrain nuclei, while astrocytes did not display any labeling. Neurons surrounding beta-amyloid deposits did not demonstrate altered expression level of BACE mRNA as compared to neurons in cortical areas that are free of beta-amyloid deposits, and the regional expression pattern of BACE mRNA did not correlate with the distribution of beta-amyloid deposits. These data suggest that high level of expression of BACE mRNA is not necessarily related to enhanced deposition of beta-amyloid plaques. To elucidate those factors that contribute to beta-amyloid plaque deposition in a particular region, the transgenic Tg2576 mouse may represent an appropriate tool.

Bigl M, Beck M, Bleyl AD, Bigl V, Eschrich K. · Institute of Biochemistry, School of Medicine, University of Leipzig, Liebigstrasse 16, D-04103, Leipzig, Germany. · Brain Res Mol Brain Res. · Pubmed #10762719 No free full text.

Abstract: In order to find out whether the increased phosphofructokinase (PFK) activities observed in brains from Alzheimer's disease (AD) patients are associated with alterations in PFK mRNA levels, we determined total PFK mRNA and the three different PFK isoenzyme mRNAs in AD and control patients by ribonuclease protection assay (RPA) and quantitative RT-PCR. PFK mRNA levels were found increased in some brain areas in AD patients. While all three PFK isoenzyme mRNAs were detectable in every studied brain sample, no changes of the PFK isoenzyme pattern were observed in patients with AD.

Bigl M, Brückner MK, Arendt T, Bigl V, Eschrich K. · Institute of Biochemistry, School of Medicine, University of Leipzig, Federal Republic of Germany. · J Neural Transm. · Pubmed #10443553 No free full text.

Abstract: The activities of hexokinase, aldolase, pyruvate kinase, lactate dehydrogenase and glucose 6-phosphate dehydrogenase were determined in brains of patients with Alzheimer's disease (AD) and in age matched controls. For pyruvate kinase and lactate dehydrogenase a significant increase in specific activity was found in frontal and temporal cortex of AD brains, while the activities of aldolase and hexokinase are not changed. Glucose 6-phosphate dehydrogenase activity was significantly reduced in hippocampus. The increase of some glycolytic enzyme activities is correlated with increased contents of lactate dehydrogenase and glial fibrillary acidic protein (GFAP) in homogenates of frontal and temporal cortex and elevated phosphofructokinase (PFK) and GFAP in astrocytes from the same brain areas. The data extend previous findings on an increase in brain PFK specific activity in AD and suggest that the increased activity of some glycolytic enzymes may be, at least in part, the result of the reactive astrocytosis developing in the course of AD.