Search

A series of tacrine-pyrazolo[3,4-b]pyridine hybrids were synthesised and evaluated as dual cholinesterase (ChE) and phosphodiesterase 4D (PDE4D) inhibitors for the treatment of Alzheimer's disease (AD). Compound 10j , which is tacrine linked with pyrazolo[3,4-b]pyridine moiety by a six-carbon spacer, was the most potent acetylcholinesterase (AChE) with IC 50 value of 0.125 μM. Moreover, compound 10j provided a desired balance of AChE and butylcholinesterase (BuChE) and PDE4D inhibition activities, with IC 50 value of 0.449 and 0.271 μM, respectively. The above results indicated that this hybrid was a promising dual functional agent for the treatment of AD. [ABSTRACT FROM AUTHOR]

Phosphodiesterase type 4D (PDE4D) has been indicated as a promising target for treating neurodegenerative pathologies such as Alzheimer's Disease (AD). By preventing cAMP hydrolysis, PDE4 inhibitors (PDE4Is) increase the cAMP response element-binding protein (CREB) phosphorylation, synaptic plasticity and long-term memory formation. Pharmacological and behavioral studies on our hit GEBR-7b demonstrated that selective PDE4DIs could improve memory without causing emesis and sedation. The hit development led to new molecule series, herein reported, characterized by a catechol structure bonded to five member heterocycles. Molecular modeling studies highlighted the pivotal role of a polar alkyl chain in conferring selective enzyme interaction. Compound 8a showed PDE4D3 selective inhibition and was able to increase intracellular cAMP levels in neuronal cells, as well as in the hippocampus of freely moving rats. Furthermore, 8a was able to readily cross the blood-brain barrier and enhanced memory performance in mice without causing any emetic-like behavior. These data support the view that PDE4D is an adequate molecular target to restore memory deficits in different neuropathologies, including AD, and also indicate compound 8a as a promising candidate for further preclinical development. [ABSTRACT FROM AUTHOR]

Memory and cognitive functions depend on the cerebral levels of cyclic adenosine monophosphate (cAMP), which are regulated by the phosphodiesterase 4 (PDE4) family of enzymes. Selected rolipram-related PDE4 inhibitors, members of the GEBR library, have been shown to increase hippocampal cAMP levels, providing pro-cognitive benefits with a safe pharmacological profile. In a recent SAR investigation involving a subset of GEBR library compounds, we have demonstrated that, depending on length and flexibility, ligands can either adopt a twisted, an extended or a protruding conformation, the latter allowing the ligand to form stabilizing contacts with the regulatory domain of the enzyme. Here, based on those findings, we describe further chemical modifications of the protruding subset of GEBR library inhibitors and their effects on ligand conformation and potency. In particular, we demonstrate that the insertion of a methyl group in the flexible linker region connecting the catechol portion and the basic end of the molecules enhances the ability of the ligand to interact with both the catalytic and the regulatory domains of the enzyme. [Display omitted] • New members of GEBR library, characterized by methylated or constrained linker chain, have been designed and synthesized. • Open chain derivatives show stronger PDE4D inhibition than the corresponding analogues lacking the methyl substituent. • On the contrary, constrained compounds show very low PDE4D inhibition. • Crystallography reveal that the methyl group points toward the bottom of the catalytic pocket increasing the binding force. • Chain flexibility is necessary in order to facilitate the interaction of the ligands with catalytic and regulatory domains. [ABSTRACT FROM AUTHOR]

Considering the importance of PDE4D inhibition and the modulation of biometals in Alzheimer's disease (AD) therapeutics, we have designed, synthesized and evaluated a series of new clioquinol-rolipram/roflumilast hybrids as multitarget-directed ligands for the treatment of AD. In vitro studies demonstrated that some of the molecules processed remarkable inhibitory activity against phosphodiesterase 4D (PDE4D), strong intracellular antioxidant capacity, potent inhibition of metal-induced aggregation of Aβ, and potential blood-brain barrier permeability. Compound 7a demonstrated significant improvement in cognitive and spatial memory in an Aβ 25-35 -induce mouse model in Morris water-maze test (MWM). These results indicate that compound 7a is a promising multifunctional candidate that is worthy of further study., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)