Modification of a promiscuous inhibitor shifts the inhibition from γ-secretase to FLT-3.

The inhibition of FLT-3 activity is an interesting target for the treatment of acute myeloid leukemia (AML). The serendipitous identification of FLT-3 inhibitors from a CK1/γ-secretase programme provided compounds with dual inhibitory activity. We analyzed the structure-activity relationship of these inhibitors and derivatized them to arrive at compounds with reduced impact on γ-secretase activity and enhanced FLT-3 inhibition.

NSAID-derived γ-secretase modulation requires an acidic moiety on the carbazole scaffold.

Modulation of γ-secretase activity holds potential for the treatment of Alzheimer's disease. Most NSAID-derived γ-secretase modulators feature a carboxylic acid, which may impair blood-brain barrier permeation. The structure activity relationship of 33 carbazoles featuring diverse carboxylic acid isosteres or metabolic precursors thereof was established in a cellular amyloid secretion assay. The modulatory activity was observed for acidic moieties and metabolically labile esters only, which supports our hypothesis of an acid-lysine interaction to be relevant for this type of γ-secretase modulators.

Inhibition of gamma-secretase by the CK1 inhibitor IC261 does not depend on CK1delta.

CK1 and gamma-secretase are interesting targets for therapeutic intervention in the treatment of cancer and Alzheimer's disease. The CK1 inhibitor IC261 was reported to inhibit gamma-secretase activity. The question is: Does CK1 inhibition directly influence gamma-secretase activity? Therefore we analyzed the SAR of 15 analogues and their impact on gamma-secretase activity. The most active compounds were investigated on CK1delta activity. These findings exclude a direct influence of CK1delta on gamma-secretase, because any change in the substitution pattern of IC261 diminished CK1 inhibition, whereas gamma-secretase inhibition is still exerted by several analogues.

NSAID-derived gamma-secretase modulators. Part III: Membrane anchoring.

Selective lowering of Abeta(42) levels with small-molecule substrate targeting gamma-secretase modulators (sGSMs), such as some non-steroidal anti-inflammatory drugs, is a promising therapeutic approach for Alzheimer's disease. Here we present N-substituted carbazole- and O-substituted fenofibrate-derived sGSMs and their activity data. Seven out of 19 screened compounds exhibited promising activity against Abeta(42) secretion at a low micromolar level. We presume that the sGSMs interact with lys624 at the membrane interface and that the lipophilic substituents anchor the compound orientation in the membrane.

Independent generation of Abeta42 and Abeta38 peptide species by gamma-secretase.

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.

Curcumin derivatives inhibit or modulate beta-amyloid precursor protein metabolism.

Curcumin-derived oxazoles and pyrazoles were synthesized in order to minimize the metal chelation properties of curcumin. The reduced rotational freedom and the absence of stereoisomers was anticipated to enhance the inhibition of gamma-secretase. Accordingly, the replacement of the 1,3-dicarbonyl moiety by isosteric heterocycles turned curcumin analogue oxazoles and pyrazoles into potent gamma-secretase inhibitors. Compounds 4a-i were found to be potent inhibitors of gamma-secretase and displayed activity in the low micromolar range.

N-Substituted carbazolyloxyacetic acids modulate Alzheimer associated gamma-secretase.

N-Sulfonylated and N-alkylated carbazolyloxyacetic acids were investigated for the inhibition and modulation of the Alzheimer's disease associated gamma-secretase. The introduction of a lipophilic substituent, which may vary from arylsulfone to alkyl, turned 2-carbazolyloxyacetic acids into potent gamma-secretase modulators. This resulted in the selective reduction of Abeta(42) and an increase of the less aggregatory Abeta(38) fragment by several compounds (e.g., 7d and 8c). Introduction of an electron donating group at position 6 and 8 of N-substituted carbazolyloxyacetic acids either decreased the activity or inversed modulation. The most active compounds displayed activity on amyloid precursor protein (APP) overexpressing cell lines in the low micromolar range and little or no effect on the gamma-secretase cleavage at the epsilon-site.

The voltage-dependent anion channel is the target for a new class of inhibitors of the mitochondrial permeability transition pore.

The relevance of the mitochondrial permeability transition pore (PTP) in Ca2+ homeostasis and cell death has gained wide attention. Yet, despite detailed functional characterization, the structure of this channel remains elusive. Here we report on a new class of inhibitors of the PTP and on the identification of their molecular target. The most potent among the compounds prepared, Ro 68-3400, inhibited PTP with a potency comparable to that of cyclosporin A. Since Ro 68-3400 has a reactive moiety capable of covalent modification of proteins, [3H]Ro 68-3400 was used as an affinity label for the identification of its protein target. In intact mitochondria isolated from rodent brain and liver and in SH-SY5Y human neuroblastoma cells, [3H]Ro 68-3400 predominantly labeled a protein of approximately 32 kDa. This protein was identified as the isoform 1 of the voltage-dependent anion channel (VDAC). Both functional and affinity labeling experiments indicated that VDAC might correspond to the site for the PTP inhibitor ubiquinone0, whereas other known PTP modulators acted at distinct sites. While Ro 68-3400 represents a new useful tool for the study of the structure and function of VDAC and the PTP, the results obtained provide direct evidence that VDAC1 is a component of this mitochondrial pore.