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Sebastian Jäger, Stefanie Leuchtenberger,
Anne Martin,
Eva Czirr,
Johanna Wesselowski,
Marco Dieckmann,
Elaine Waldron,
Carsten Korth,
Edward H Koo,
Michael Heneka,
Sascha Weggen,
Claus U Pietrzik
[show abstract]
[hide abstract]
ABSTRACT: The Swedish mutation within the amyloid precursor protein (APP) causes early-onset Alzheimer's disease due to increased cleavage of APP by BACE1. While beta-secretase shedding of Swedish APP (APPswe) largely results from an activity localized in the late secretory pathway, cleavage of wild-type APP occurs mainly in endocytic compartments. However, we show that liberation of Abeta from APPswe is still dependent on functional internalization from the cell surface. Inspite the unchanged overall beta-secretase cleaved soluble APP released from APP(swe) secretion, mutations of the APPswe internalization motif strongly reduced C99 levels and substantially decreased Abeta secretion. We point out that alpha-secretase activity-mediated conversion of C99 to C83 is the main cause of this Abeta reduction. Furthermore, we demonstrate that alpha-secretase cleavage of C99 even contributes to the reduction of Abeta secretion of internalization deficient wild-type APP. Therefore, inhibition of alpha-secretase cleavage increased Abeta secretion through diminished conversion of C99 to C83 in APP695, APP695swe or C99 expressing cells.
Journal of Neurochemistry 10/2009; 111(6):1369-82. · 4.06 Impact Factor
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Eva Czirr,
Barbara A Cottrell, Stefanie Leuchtenberger,
Thomas Kukar,
Thomas B Ladd,
Hermann Esselmann,
Sabine Paul,
Robert Schubenel,
Justin W Torpey,
Claus U Pietrzik,
Todd E Golde,
Jens Wiltfang,
Karlheinz Baumann,
Edward H Koo,
Sascha Weggen
[show abstract]
[hide abstract]
ABSTRACT: Proteolytic processing of the amyloid precursor protein by beta- and gamma-secretase generates the amyloid-beta (Abeta) peptides, which are principal drug targets in Alzheimer disease therapeutics. gamma-Secretase has imprecise cleavage specificity and generates the most abundant Abeta40 and Abeta42 species together with longer and shorter peptides such as Abeta38. Several mechanisms could explain the production of multiple Abeta peptides by gamma-secretase, including sequential processing of longer into shorter Abeta peptides. A novel class of gamma-secretase modulators (GSMs) that includes some non-steroidal anti-inflammatory drugs has been shown to selectively lower Abeta42 levels without a change in Abeta40 levels. A signature of GSMs is the concomitant increase in shorter Abeta peptides, such as Abeta38, leading to the suggestion that generation of Abeta42 and Abeta38 peptide species by gamma-secretase is coordinately regulated. However, no evidence for or against such a precursor-product relationship has been provided. We have previously shown that stable overexpression of aggressive presenilin-1 (PS1) mutations associated with early-onset familial Alzheimer disease attenuated the cellular response to GSMs, resulting in greatly diminished Abeta42 reductions as compared with wild type PS1. We have now used this model system to investigate whether Abeta38 production would be similarly affected indicating coupled generation of Abeta42 and Abeta38 peptides. Surprisingly, treatment with the GSM sulindac sulfide increased Abeta38 production to similar levels in four different PS1 mutant cell lines as compared with wild type PS1 cells. This was confirmed with the structurally divergent GSMs ibuprofen and indomethacin. Mass spectrometry analysis and high resolution urea gel electrophoresis further demonstrated that sulindac sulfide did not induce detectable compensatory changes in levels of other Abeta peptide species. These data provide evidence that Abeta42 and Abeta38 species can be independently generated by gamma-secretase and argue against a precursor-product relationship between these peptides.
Journal of Biological Chemistry 07/2008; 283(25):17049-54. · 4.77 Impact Factor
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Eva Czirr,
Barbara A. Cottrell, Stefanie Leuchtenberger,
Thomas Kukar,
Thomas B. Ladd,
Hermann Esselmann,
Sabine Paul,
Robert Schubenel,
Justin W. Torpey,
Claus U. Pietrzik,
Todd E. Golde,
Jens Wiltfang,
Karlheinz Baumann,
Edward H. Koo,
Sascha Weggen
[show abstract]
[hide abstract]
ABSTRACT: Proteolytic processing of the amyloid precursor protein by β- and γ-secretase generates the amyloid-β (Aβ) peptides, which
are principal drug targets in Alzheimer disease therapeutics. γ-Secretase has imprecise cleavage specificity and generates
themostabundant Aβ40 and Aβ42 species together with longer and shorter peptides such as Aβ38. Several mechanisms could explain
the production of multiple Aβ peptides by γ-secretase, including sequential processing of longer into shorter Aβ peptides.
A novel class of γ-secretase modulators (GSMs) that includes some non-steroidal anti-inflammatory drugs has been shown to
selectively lower Aβ42 levels without a change in Aβ40 levels. A signature of GSMs is the concomitant increase in shorter
Aβ peptides, such as Aβ38, leading to the suggestion that generation of Aβ42 and Aβ38 peptide species by γ-secretase is coordinately
regulated. However, no evidence for or against such a precursor-product relationship has been provided. We have previously
shown that stable overexpression of aggressive presenilin-1 (PS1) mutations associated with early-onset familial Alzheimer
disease attenuated the cellular response to GSMs, resulting in greatly diminished Aβ42 reductions as compared with wild type
PS1. We have now used this model system to investigate whether Aβ38 production would be similarly affected indicating coupled
generation of Aβ42 and Aβ38 peptides. Surprisingly, treatment with the GSM sulindac sulfide increased Aβ38 production to similar
levels in four different PS1 mutant cell lines as compared with wild type PS1 cells. This was confirmed with the structurally
divergent GSMs ibuprofen and indomethacin. Mass spectrometry analysis and high resolution urea gel electrophoresis further
demonstrated that sulindac sulfide did not induce detectable compensatory changes in levels of other Aβ peptide species. These
data provide evidence that Aβ42 and Aβ38 species can be independently generated by γ-secretase and argue against a precursor-product
relationship between these peptides.
Journal of Biological Chemistry 06/2008; 283(25):17049-17054. · 4.77 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Epidemiological studies have suggested that long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with a reduced incidence of Alzheimer's disease (AD). Several mechanisms have been proposed to explain these findings including increased shedding of the soluble ectodomain of the amyloid precursor protein (sAPP), which functions as a neurotrophic and neuroprotective factor in vitroand in vivo.
To clarify whether NSAIDs consistently stimulate sAPP secretion.
293-EBNA cells with stable overexpression of an APP-alkaline phosphatase fusion protein (APP-AP), SH-SY5Y and PC12 cells or primary telencephalic chicken neurons were treated with ibuprofen or indomethacin. APP shedding was then determined by measuring AP activity in conditioned media, Western blot analysis with antibodies against total sAPP or specific for sAPP-alpha, or in a pulse-chase paradigm.
AP activity in conditioned media was not increased after NSAID treatment of 293-EBNA cells whereas it was elevated by phorbol ester. Surprisingly, ibuprofen or indomethacin treatment of SH-SY5Y and PC12 cells expressing endogenous APP did not cause changes in sAPP or sAPP-alpha secretion or downregulation of cellular APP. These findings were further corroborated in primary chicken neuronal cultures.
Using various experimental settings, we were unable to confirm sAPP or sAPP-alpha stimulation with the NSAIDs ibuprofen and indomethacin in transfected and nontransfected cells of neuronal and nonneuronal origin. Importantly, these findings seem to rule out chronic sAPP stimulation as an alternative mechanism of NSAID action in AD.
Neurodegenerative Diseases 04/2008; 6(1-2):1-8. · 3.06 Impact Factor
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[show abstract]
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ABSTRACT: Curcumin binds to the amyloid beta peptide (Abeta) and inhibits or modulates amyloid precursor protein (APP) metabolism. Therefore, curcumin-derived isoxazoles and pyrazoles were synthesized to minimize the metal chelation properties of curcumin. The decreased rotational freedom and absence of stereoisomers was predicted to enhance affinity toward Abeta(42) aggregates. Accordingly, replacement of the 1,3-dicarbonyl moiety with isosteric heterocycles turned curcumin analogue isoxazoles and pyrazoles into potent ligands of fibrillar Abeta(42) aggregates. Additionally, several compounds are potent inhibitors of tau protein aggregation and depolymerized tau protein aggregates at low micromolar concentrations.
ChemMedChem 02/2008; 3(1):165-72. · 3.15 Impact Factor
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[show abstract]
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ABSTRACT: Nonsteroidal anti-inflammatory drugs (NSAIDs) have been considered for the treatment and prevention of Alzheimer’s disease
(AD) for more than two decades. The rationale for this approach is derived from epidemiological studies and from the observation
that the causative amyloid pathology in the AD brain is accompanied by a secondary inflammatory response. Given that the primary
pharmacological targets of NSAIDs are cyclooxygenases (COX), the reduced expression of inflammatory markers in AD mouse models
after peripheral administration of NSAIDs has suggested that these compounds may be beneficial in AD by inhibiting a wide
range of inflammatory responses in the central nervous system.
12/2007: pages 167-193;
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[show abstract]
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ABSTRACT: Abeta42-lowering nonsteroidal anti-inflammatory drugs (NSAIDs) constitute the founding members of a new class of gamma-secretase modulators that avoid side effects of pan-gamma-secretase inhibitors on NOTCH processing and function, holding promise as potential disease-modifying agents for Alzheimer disease (AD). These modulators are active in cell-free gamma-secretase assays indicating that they directly target the gamma-secretase complex. Additional support for this hypothesis was provided by the observation that certain mutations in presenilin-1 (PS1) associated with early-onset familial AD (FAD) change the cellular drug response to Abeta42-lowering NSAIDs. Of particular interest is the PS1-DeltaExon9 mutation, which provokes a pathogenic increase in the Abeta42/Abeta40 ratio and dramatically reduces the cellular response to the Abeta42-lowering NSAID sulindac sulfide. This FAD PS1 mutant is unusual as a splice-site mutation results in deletion of amino acids Thr(291)-Ser(319) including the endoproteolytic cleavage site of PS1, and an additional amino acid exchange (S290C) at the exon 8/10 splice junction. By genetic dissection of the PS1-DeltaExon9 mutation, we now demonstrate that a synergistic effect of the S290C mutation and the lack of endoproteolytic cleavage is sufficient to elevate the Abeta42/Abeta40 ratio and that the attenuated response to sulindac sulfide results partially from the deficiency in endoproteolysis. Importantly, a wider screen revealed that a diminished response to Abeta42-lowering NSAIDs is common among aggressive FAD PS1 mutations. Surprisingly, these mutations were also partially unresponsive to gamma-secretase inhibitors of different structural classes. This was confirmed in a mouse model with transgenic expression of the PS1-L166P mutation, in which the potent gamma-secretase inhibitor LY-411575 failed to reduce brain levels of soluble Abeta42. In summary, these findings highlight the importance of genetic background in drug discovery efforts aimed at gamma-secretase, suggesting that certain AD mouse models harboring aggressive PS mutations may not be informative in assessing in vivo effects of gamma-secretase modulators and inhibitors.
Journal of Biological Chemistry 09/2007; 282(34):24504-13. · 4.77 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Aβ42-lowering nonsteroidal anti-inflammatory drugs (NSAIDs) constitute the founding members of a new class of γ-secretase
modulators that avoid side effects of pan-γ-secretase inhibitors on NOTCH processing and function, holding promise as potential
disease-modifying agents for Alzheimer disease (AD). These modulators are active in cell-free γ-secretase assays indicating
that they directly target the γ-secretase complex. Additional support for this hypothesis was provided by the observation
that certain mutations in presenilin-1 (PS1) associated with early-onset familial AD (FAD) change the cellular drug response
to Aβ42-lowering NSAIDs. Of particular interest is the PS1-ΔExon9 mutation, which provokes a pathogenic increase in the Aβ42/Aβ40
ratio and dramatically reduces the cellular response to the Aβ42-lowering NSAID sulindac sulfide. This FAD PS1 mutant is unusual
as a splice-site mutation results in deletion of amino acids Thr291–Ser319 including the endoproteolytic cleavage site of PS1, and an additional amino acid exchange (S290C) at the exon 8/10 splice
junction. By genetic dissection of the PS1-ΔExon9 mutation, we now demonstrate that a synergistic effect of the S290C mutation
and the lack of endoproteolytic cleavage is sufficient to elevate the Aβ42/Aβ40 ratio and that the attenuated response to
sulindac sulfide results partially from the deficiency in endoproteolysis. Importantly, a wider screen revealed that a diminished
response to Aβ42-lowering NSAIDs is common among aggressive FAD PS1 mutations. Surprisingly, these mutations were also partially
unresponsive to γ-secretase inhibitors of different structural classes. This was confirmed in a mouse model with transgenic
expression of the PS1-L166P mutation, in which the potent γ-secretase inhibitor LY-411575 failed to reduce brain levels of
soluble Aβ42. In summary, these findings highlight the importance of genetic background in drug discovery efforts aimed at
γ-secretase, suggesting that certain AD mouse models harboring aggressive PS mutations may not be informative in assessing
in vivo effects of γ-secretase modulators and inhibitors.
Journal of Biological Chemistry 08/2007; 282(34):24504-24513. · 4.77 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The amyloid-beta (Abeta) peptides and in particular the longer, highly amyloidogenic isoform Abeta42 are believed by many to be the central disease-causing agents in Alzheimer's disease (AD). Consequently, academic and pharmaceutical laboratories have focused on elucidating the mechanisms of Abeta production and developing strategies to diminish Abeta formation for treatment or prevention of AD. The most substantial advances have been made with respect to inhibitors of the gamma-secretase enzyme, which catalyzes the final step in the generation of Abeta from the amyloid precursor protein (APP). Highly potent gamma-secretase inhibitors which suppress production of all Abeta peptides are available today. However, due to the promiscuous substrate specificity of gamma-secretase and its essential role in the NOTCH signaling pathway overt mechanism-based toxicity has been observed in preclinical studies of gamma-secretase inhibitors. For that reason, specific blockage of Abeta42 production might be preferable over non-discriminatory gamma-secretase inhibition but small molecule inhibitors of Abeta42 production have remained elusive until recently. This has changed with the discovery that certain non-steroidal anti-inflammatory drugs (NSAIDs) including ibuprofen possess preferential Abeta42-lowering activity. These compounds seem to offer a window of modulation where Abeta42 production is potently inhibited whereas processing of the NOTCH receptor and other gamma-secretase substrates remains unaffected. The Abeta42-lowering activity of NSAIDs is not related to inhibition of cyclooxygenases and can be dissociated from the anti-inflammatory properties of this class of drugs. Ongoing efforts concentrate on uncovering the mechanism of action and improving potency and brain permeability of Abeta42-lowering compounds. Hopes are high that in the near future this will lead to the development of clinically viable compounds which selectively target Abeta42 as a key molecule in the pathogenesis of AD.
Current pharmaceutical design 02/2006; 12(33):4337-55. · 4.41 Impact Factor
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Stefanie Leuchtenberger,
Markus P Kummer,
Thomas Kukar,
Eva Czirr,
Nicole Teusch,
Sarah A Sagi,
Rebecca Berdeaux,
Claus U Pietrzik,
Thomas B Ladd,
Todd E Golde,
Edward H Koo,
Sascha Weggen
[show abstract]
[hide abstract]
ABSTRACT: Certain non-steroidal anti-inflammatory drugs (NSAIDs) preferentially inhibit production of the amyloidogenic Abeta42 peptide, presumably by direct modulation of gamma-secretase activity. A recent report indicated that NSAIDs could reduce Abeta42 by inhibition of the small GTPase Rho, and a single inhibitor of Rho kinase (ROCK) mimicked the effects of Abeta42-lowering NSAIDs. To investigate whether Abeta42 reduction is a common property of ROCK inhibitors, we tested commercially available compounds in cell lines that were previously used to demonstrate the Abeta42-lowering activity of NSAIDs. Surprisingly, we found that two ROCK inhibitors reduced total Abeta secretion in a dose-dependent manner but showed no selectivity for Abeta42. In addition, ROCK inhibitors did not increase Abeta38 secretion in cell-based assays or reduce Abeta production in gamma-secretase in vitro assays, which are critical characteristics of Abeta42-lowering NSAIDs. The reduction in total Abeta levels by ROCK inhibitors was not accompanied by overall-changes in amyloid precursor protein processing. Targeting ROCK by expression of dominant-negative or constitutively active ROCK mutants failed to modulate Abeta secretion, indicating that ROCK inhibition may either be redundant or insufficient for Abeta reduction by ROCK inhibitors. Taken together, these results seem to exclude a mechanistic involvement of ROCK in the Abeta42-lowering activity of NSAIDs.
Journal of Neurochemistry 02/2006; 96(2):355-65. · 4.06 Impact Factor
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Stefanie Leuchtenberger,
Markus P. Kummer,
Thomas Kukar,
Eva Czirr,
Nicole Teusch,
Sarah A. Sagi,
Rebecca Berdeaux,
Claus U. Pietrzik,
Thomas B. Ladd,
Todd E. Golde,
Edward H. Koo,
Sascha Weggen
[show abstract]
[hide abstract]
ABSTRACT: Certain non-steroidal anti-inflammatory drugs (NSAIDs) preferentially inhibit production of the amyloidogenic Aβ42 peptide, presumably by direct modulation of γ-secretase activity. A recent report indicated that NSAIDs could reduce Aβ42 by inhibition of the small GTPase Rho, and a single inhibitor of Rho kinase (ROCK) mimicked the effects of Aβ42-lowering NSAIDs. To investigate whether Aβ42 reduction is a common property of ROCK inhibitors, we tested commercially available compounds in cell lines that were previously used to demonstrate the Aβ42-lowering activity of NSAIDs. Surprisingly, we found that two ROCK inhibitors reduced total Aβ secretion in a dose-dependent manner but showed no selectivity for Aβ42. In addition, ROCK inhibitors did not increase Aβ38 secretion in cell-based assays or reduce Aβ production in γ-secretase in vitro assays, which are critical characteristics of Aβ42-lowering NSAIDs. The reduction in total Aβ levels by ROCK inhibitors was not accompanied by overall-changes in amyloid precursor protein processing. Targeting ROCK by expression of dominant-negative or constitutively active ROCK mutants failed to modulate Aβ secretion, indicating that ROCK inhibition may either be redundant or insufficient for Aβ reduction by ROCK inhibitors. Taken together, these results seem to exclude a mechanistic involvement of ROCK in the Aβ42-lowering activity of NSAIDs.
Journal of Neurochemistry 11/2005; 96(2):355 - 365. · 4.06 Impact Factor
