(Hetero-)(arylidene)arylhydrazides as Multitarget-Directed Monoamine Oxidase Inhibitors

Latest advances in dual inhibitors of acetylcholinesterase and monoamine oxidase B against Alzheimer's disease

Alzheimer's disease (AD) is a progressive brain disease characterised by progressive memory loss and cognition impairment, ultimately leading to death. There are three FDA-approved acetylcholinesterase inhibitors (donepezil, rivastigmine, and galantamine, AChEIs) for the symptomatic treatment of AD. Monoamine oxidase B (MAO-B) has been considered to contribute to pathologies of AD. Therefore, we reviewed the dual inhibitors of acetylcholinesterase (AChE) and MAO-B developed in the last five years. In this review, these dual-target inhibitors were classified into six groups according to the basic parent structure, including chalcone, coumarin, chromone, benzo-fused five-membered ring, imine and hydrazine, and other scaffolds. Their design strategies, structure-activity relationships (SARs), and molecular docking studies with AChE and MAO-B were analysed and discussed, giving valuable insights for the subsequent development of AChE and MAO-B dual inhibitors. Challenges in the development of balanced and potent AChE and MAO-B dual inhibitors were noted, and corresponding solutions were provided.

Xanthine-Dopamine Hybrid Molecules as Multitarget Drugs with Potential for the Treatment of Neurodegenerative Diseases

Multitarget drugs based on a hybrid dopamine-xanthine core were designed as potential drug candidates for the treatment of neurodegenerative diseases. Monoamine oxidase B (MAO-B) inhibitors with significant ancillary A_2A adenosine receptor (A_2AAR) antagonistic properties were further developed to exhibit additional phosphodiesterase-4 and -10 (PDE4/10) inhibition and/or dopamine D₂ receptor (D₂R) agonistic activity. While all of the designed compounds showed MAO-B inhibition in the nanomolar range mostly combined with submicromolar A_2AAR affinity, significant enhancement of PDE-inhibitory and D₂R-agonistic activity was additionally reached for some compounds through various structural modifications. The final multitarget drugs also showed promising antioxidant properties in vitro. In order to evaluate their potential neuroprotective effect, representative ligands were tested in a cellular model of toxin-induced neurotoxicity. As a result, protective effects against oxidative stress in neuroblastoma cells were observed, confirming the utility of the applied strategy. Further evaluation of the newly developed multitarget ligands in preclinical models of Alzheimer's and Parkinson's diseases is warranted.

The Role of Mitochondrial Genes in Neurodegenerative Disorders

Mitochondrial disorders are clinically heterogeneous, resulting from nuclear gene and mitochondrial mutations that disturb the mitochondrial functions and dynamics. There is a lack of evidence linking mtDNA mutations to neurodegenerative disorders, mainly due to the absence of noticeable neuropathological lesions in postmortem samples. This review describes various gene mutations in Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, multiple sclerosis, and stroke. These abnormalities, including PINK1, Parkin, and SOD1 mutations, seem to reveal mitochondrial dysfunctions due to either mtDNA mutation or deletion, the mechanism of which remains unclear in depth.

Replacement of Chalcone-Ethers with Chalcone-Thioethers as Potent and Highly Selective Monoamine Oxidase-B Inhibitors and Their Protein-Ligand Interactions

To develop new potent and highly selective MAO-B inhibitors from chalcone-thioethers, eleven chalcones-thioethers were synthesized and their monoamine oxidase (MAO) inhibition, kinetics, reversibility, and cytotoxicity of lead compounds were analyzed. Molecular dynamics were carried out to investigate the interactions. Compound TM8 showed potent inhibitory activity against MAO-B, with an IC₅₀ value of 0.010 µM, followed by TM1, TM2, TM7, and TM10 (IC₅₀ = 0.017, 0.021, 0.023, and 0.026 µM, respectively). Interestingly, TM8 had an extremely high selectivity index (SI; 4860) for MAO-B. Reversibility and kinetic experiments showed that TM8 and TM1 were reversible and competitive inhibitors of MAO-B with K_i values of 0.0031 ± 0.0013 and 0.011± 0.001 µM, respectively. Both TM1 and TM8 were non-toxic to Vero cells with IC₅₀ values of 241.8 and 116.3 µg/mL (i.e., 947.7 and 402.4 µM), respectively, and at these IC₅₀ values, both significantly reduced reactive oxygen species (ROS) levels. TM1 and TM8 showed high blood-brain barrier permeabilities in the parallel artificial membrane permeability assay. Molecular dynamics studies were conducted to investigate interactions between TM1 and TM8 and the active site of MAO-B. Conclusively, TM8 and TM1 are potent and highly selective MAO-B inhibitors with little toxicity and good ROS scavenging abilities and it is suggested that both are attractive prospective candidates for the treatment of neurological disorders.