New multitarget molecules derived from caffeine as modulators of the cholinergic system

Abstract

Cholinergic deficit is a characteristic factor of Alzheimer's disease. Two possible molecular targets for its treatment are the acetylcholinesterase (AChE) and the nicotinic acetylcholine receptors (nAChR). In previous studies, we found that caffeine behaves as a partial nAChR agonist and confirmed that it inhibits AChE. Based on these findings, in this work we obtained 8 more potent bifunctional derivatives for these molecular targets. They consisted of a theophylline ring connected to several chemical groups (pyrrole, piperidine, methylpiperazine, or diethylamine) by different linkers (linear chains of 5 and 7 carbon atoms (C5 and C7) or C3-NH-C2 and C5-NH-C2 chains). All of them were more potent AChE inhibitors than caffeine. Electrophysiological studies by single-channel measurements in adult muscle nAChR transiently expressed in BOSC23 cells showed that all compounds, except C5 and C7 diethylamine, activated the nAChR, being C7-piperidine the most active. To understand the molecular mechanism underlying receptor activation, we further explored whether these analogs influence the conformational state of nAChR using nAChR-rich membranes of T. californica and crystal violet (CrV), a sensitive probe for the conformation of nAChRs. We observed that only C5-piperidine stabilized the nAChR in a desensitized state. Finally, we carried out in silico studies on AChE and nAChR (with its loop C partially closed) to obtain information on the molecular interactions among these compounds and both molecular targets. Altogether, our results show that the new synthetized compounds can inhibit the AChE and activate the nAChR with greater potency than caffeine and provide further information on the modulation mechanisms of pharmacological targets for the design of novel therapeutic interventions in neurological diseases.