Caudo-rostral brain spreading of α-synuclein through vagal connections.

α-Synuclein accumulation and pathology in Parkinson's disease typically display a caudo-rostral pattern of progression, involving neuronal nuclei in the medulla oblongata at the earliest stages. In this study, selective expression and accumulation of human α-synuclein within medullary neurons was achieved via retrograde transport of adeno-associated viral vectors unilaterally injected into the vagus nerve in the rat neck. The exogenous protein progressively spread toward more rostral brain regions where it could be detected within axonal projections. Propagation to the pons, midbrain and forebrain followed a stereotypical pattern of topographical distribution. It affected areas such as the coeruleus-subcoeruleus complex, dorsal raphae, hypothalamus and amygdala ipsilateral and, to a lesser extent, contralateral to the injection side. Spreading was accompanied by evidence of neuritic pathology in the form of axonal varicosities intensely immunoreactive for human α-synuclein and containing Thioflavin-S-positive fibrils. Thus, overexpression of human α-synuclein in the lower brainstem is sufficient to induce its long-distance caudo-rostral propagation, recapitulating features of Parkinson's disease and mechanisms of disease progression.

Generation of Abeta38 and Abeta42 is independently and differentially affected by familial Alzheimer disease-associated presenilin mutations and gamma-secretase modulation.

Alzheimer disease amyloid beta-peptide (Abeta) is generated via proteolytic processing of the beta-amyloid precursor protein by beta- and gamma-secretase. Gamma-secretase can be blocked by selective inhibitors but can also be modulated by a subset of non-steroidal anti-inflammatory drugs, including sulindac sulfide. These drugs selectively reduce the generation of the aggregation-prone 42-amino acid Abeta(42) and concomitantly increase the levels of the rather benign Abeta(38). Here we show that Abeta(42) and Abeta(38) generation occur independently from each other. The amount of Abeta(42) produced by cells expressing 10 different familial Alzheimer disease (FAD)-associated mutations in presenilin (PS) 1, the catalytic subunit of gamma-secretase, appeared to correlate with the respective age of onset in patients. However, Abeta(38) levels did not show a negative correlation with the age of onset. Modulation of gamma-secretase activity by sulindac sulfide reduced Abeta(42) in the case of wild type PS1 and two FAD-associated PS1 mutations (M146L and A285V). The remaining eight PS1 FAD mutants showed either no reduction of Abeta(42) or only rather subtle effects. Strikingly, even the mutations that showed no effect on Abeta(42) levels allowed a robust increase of Abeta(38) upon treatment with sulindac sulfide. Similar observations were made for fenofibrate, a compound known to increase Abeta(42) and to decrease Abeta(38). For mutants that predominantly produce Abeta(42), the ability of fenofibrate to further increase Abeta(42) levels became diminished, whereas Abeta(38) levels were altered to varying extents for all mutants analyzed. Thus, we conclude that Abeta(38) and Abeta(42) production do not depend on each other. Using an independent non-steroidal anti-inflammatory drug derivative, we obtained similar results for PS1 as well as for PS2. These in vitro results were confirmed by in vivo experiments in transgenic mice expressing the PS2 N141I FAD mutant. Our findings therefore have strong implications on the selection of transgenic mouse models used for screening of the Abeta(42)-lowering capacity of gamma-secretase modulators. Furthermore, human patients with certain PS mutations may not respond to gamma-secretase modulators.

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.

Scaffold of the cyclooxygenase-2 (COX-2) inhibitor carprofen provides Alzheimer gamma-secretase modulators.

N-sulfonylated and N-alkylated carprofen derivatives were investigated for their inhibition and modulation of gamma-secretase, which is associated with Alzheimer's disease. The introduction of a lipophilic substituent transformed the COX-2 inhibitor carprofen into a potent gamma-secretase modulator. Several compounds (e.g., 9p, 11f) caused selective reduction of Abeta42 and an increase of Abeta38. The most active compounds displayed activities in the low micromolar range and no effect on the gamma-secretase cleavage at the e-site.

Catalytic site-directed gamma-secretase complex inhibitors do not discriminate pharmacologically between Notch S3 and beta-APP cleavages.

The generation of gamma-secretase inhibitors which block the release of beta-amyloid peptide (Abeta) has long been an attractive therapeutic avenue for treatment or prevention of Alzheimer's disease (AD). Such inhibitors would reduce levels of Abeta available for aggregation into toxic assemblies that lead to the plaque pathology found in affected brain tissue. Cumulative evidence suggests that the S3 cleavage of Notch is also dependent on presenilins (PS) and is carried out by the multimeric PS-containing gamma-secretase complex. It is therefore possible that Notch function could be affected by gamma-secretase inhibitors. To assess the relationship between the cleavage of these substrates in the same system, Western blot cleavage assays have been established using a human cell line stably expressing both the beta-amyloid precursor protein (beta-APP) and the truncated Notch1 receptor fragment NotchDeltaE. Thus, a direct correlation may be made, following inhibitor treatment, of the decrease in the levels of the cleavage products, Abeta peptide and the Notch intracellular domain (NICD), as well as the increase in stabilized levels of both substrates. This analysis has been performed with a range of selected gamma-secretase inhibitors from six distinct structural classes. Changes in all four species usually occur in concert and with remarkably good agreement. A significant cleavage window is not clearly apparent in any case. Thus, these Notch and beta-APP cleavages cannot be dissected apart easily since they show the same pharmacological profile of inhibition. Whether this translates into proportionally reduced Notch signaling in vivo, however, remains to be seen.

Effect of PVP K-25 on the formation of the naproxen:beta-ciclodextrin complex.

The aim of this study was to investigate the effects of the presence of the water-soluble polymer polyvinylpyrrolidone K-25 (MW=24000g/mol) on the complexation of the AINE naproxen, in its sodium salt form, with the beta-cyclodextrin. The data revealed that the polyvinylpyrrolidone K-25 interacts with the drug as well as with the drug:beta-cyclodextrin inclusion complex. The polymer shows more affinity for the inclusion complex, K=(6.67+/-0.292) x 10(-5)M(-1) than for the free drug, (2.08+/-0.208) x 10(-5)M(-1). The presence of different proportions of polymer, in a range 0-1% (w/w) of polyvinylpyrrolidone, does not increase the ability of drug-cyclodextrin complexation but important changes in the driving force of complex formation were detected, depending on the percentage of polyvinylpyrrolidone K-25 present. At low polymer concentrations, the complexation process is driven entropically, while at higher PVP proportions it is enthalpically favored. In the ternary system, polyvinylpyrrolidone K-25 partially or totally coats the drug:beta-cyclodextrin inclusion complex interacting with the beta-cyclodextrin (through hydrogen bonds), and with the naproxen.