(1032-A) Development of novel thiosemicarbazones as multi-target directed ligands for the treatment of Alzheimer’s disease

Abstract: Alzheimer’s disease (AD) is a devastating neurodegenerative disorder affecting mental ability and interrupts neurocognitive functions. Treating multifactorial conditions of AD with a single-target-directed drug is highly difficult. Thus, a multi-target-directed ligand (MTDL) development strategy has been developed as a promising approach for the treatment of AD.

Herein, we have synthesized series of thiosemicarbazones (1-20) as MTDLs and reported their bioactivities against diverse neuropathological events involved in the AD. In vitro studies revealed that two compounds exhibited good anticholinesterase activity [compound-4 (IC50 = 15.98 µM) and compound-7 (IC50 = 30.23 µM)], well supported by a detailed computational study. Both analogs have shown good thermodynamic behaviour and stability through interactions with characteristic amino acid residues throughout simulations of 100 ns.

Later, we have investigated N-methyl-D-aspartate receptors (NMDARs) channel-blocking activity of selected synthesized compounds using electrophysiological recordings in Xenopus laevis oocytes. Selected analogs were tested against four GluN2 subunits (GluN2A through GluN2D), coexpressing each of them with the obligatory GluN1-1a subunit. Electrophysiological assay was employed to analyze cationic currents generated by Na+ and Ca2+ influx as well as inhibition of these currents by synthesized compounds as plausible NMDAR antagonists. These analogs have shown characteristic inhibitory response against the GluN1-1a + GluN2B subunit of NMDAR [compound-4 (IC50 = 89.43 µM) and compound-7 (IC50 = 118.6 µM)], with preference over other GluN2 subtypes, and may serve as a starting point for the development of GluN2B subtype antagonists for the treatment of AD.

Pre-treatment of BV-2 microglial cells with compound-4 and compound-7 effectively decreased nitrite production compared to nitrite produced by lipopolysaccharide-treated cells alone. Further, the effect of both analogs on autophagy regulation was also determined using stably transfected SH-SY5Y neuroblastoma cells. Compound-4 significantly enhanced the autophagy flux in neuroblastoma cells. A significant decrease in copper-catalyzed oxidation of amyloid-β in presence of synthesized thiosemicarbazones was also observed.

Collectively, our findings indicate that these analogs have potential as effective anti-AD candidates and can be used as a prototype to develop more safer multi-targeted anti-AD drugs.