1,4-Substituted 4-(1H)-pyridylene-hydrazone-type inhibitors of AChE, BuChE, and amyloid-ß aggregation crossing the blood-brain barrier.

Given the fundamentally multifactorial character of Alzheimer's disease (AD), addressing more than one target for disease modification or therapy is expected to be highly advantageous. Here, following the cholinergic hypothesis, we aimed to inhibit both acetyl- and butyrylcholinesterase (AChE and BuChE) in order to increase the concentration of acetylcholine in the synaptic cleft. In addition, the formation of the amyloid ß fibrils should be inhibited and already preformed fibrils should be destroyed. Based on a recently identified AChE inhibitor with a 1,4-substituted 4-(1H)-pyridylene-hydrazone skeleton, a substance library has been generated and tested for inhibition of AChE, BuChE, and fibril formation. Blood-brain barrier mobility was ensured by a transwell assay. Whereas the p-nitrosubstituted compound 18C shows an anti-AChE activity in the nanomolar range of concentration (IC50=90 nM), the bisnaphthyl substituted compound 20L was found to be the best overall inhibitor of AChE/BuChE and enhances the fibril destruction.

Mitochondrion-derived reactive oxygen species lead to enhanced amyloid beta formation.

AIMS: Intracellular amyloid beta (Aß) oligomers and extracellular Aß plaques are key players in the progression of sporadic Alzheimer's disease (AD). Still, the molecular signals triggering Aß production are largely unclear. We asked whether mitochondrion-derived reactive oxygen species (ROS) are sufficient to increase Aß generation and thereby initiate a vicious cycle further impairing mitochondrial function. RESULTS: Complex I and III dysfunction was induced in a cell model using the respiratory inhibitors rotenone and antimycin, resulting in mitochondrial dysfunction and enhanced ROS levels. Both treatments lead to elevated levels of Aß. Presence of an antioxidant rescued mitochondrial function and reduced formation of Aß, demonstrating that the observed effects depended on ROS. Conversely, cells overproducing Aß showed impairment of mitochondrial function such as comprised mitochondrial respiration, strongly altered morphology, and reduced intracellular mobility of mitochondria. Again, the capability of these cells to generate Aß was partly reduced by an antioxidant, indicating that Aß formation was also ROS dependent. Moreover, mice with a genetic defect in complex I, or AD mice treated with a complex I inhibitor, showed enhanced Aß levels in vivo. INNOVATION: We show for the first time that mitochondrion-derived ROS are sufficient to trigger Aß production in vitro and in vivo. CONCLUSION: Several lines of evidence show that mitochondrion-derived ROS result in enhanced amyloidogenic amyloid precursor protein processing, and that Aß itself leads to mitochondrial dysfunction and increased ROS levels. We propose that starting from mitochondrial dysfunction a vicious cycle is triggered that contributes to the pathogenesis of sporadic AD.