ALL YOU NEED IS COFFEE

FABIANI, C.; CORRADI, J.; ANTOLLINI, S.S.

Buenos Aires

Congreso; Reunión Conjunta de Sociedades Biomédicas; 2017

Cholinergic deficit is regarded as an important factor responsiblefor Alzheimer?s disease symptoms. Two molecular targets for thetreatment of this disease are acetylcholinesterase (AChE) and nicotinicreceptor (nAChR). Caffeine (CAFF) acts as a non-competitiveinhibitor of AChE but its mechanism of action on nAChR is still unknown.To this end, we first explored if CAFF influences the nAChRconformational state using the AChR conformational-sensitive probecrystal violet (CrV) and AChR-rich membranes from T. californica.CAFF induced changes in the KD value of CrV in a concentration-dependentmanner taking the nAChR to a state close to thedesensitized one. In the presence of α-bungarotoxin, a specific nAChRcompetitive antagonist, high concentrations of CAFF increasedthe KD value of CrV, compatible with a competition for the CrV sitein the channel pore. The same effect was seen with galantamine,an AChE inhibitor and partial agonist of nAChR. To understand themolecular mechanism underlying the conformational changes ofthe nAChR, we expressed adult muscle or neuronal a7 nAChRs inBOSC cells, and performed single channel recordings with differentCAFF concentrations in the presence or absence of ACh. At lowconcentrations (1-300 µM), CAFF activated muscle and a7 nAChRs,and the activation profile was independent of CAFF concentration.On the other hand, at high CAFF concentrations (up to 20 mM),the mean open duration decreased, the relative area of the brieferclosed component and the cluster duration increased, and a flickeringbehavior was observed, these suggesting that CAFF acts asan open channel blocker. Thus, we here demonstrate a dual effectof CAFF on muscle and a7 nAChRs, behaving as a weak agonistat low concentrations and as a negative modulator at high concentrations.Our results bring new information about the mechanism ofmodulation of pharmacology targets for the design of new therapiesfor the intervention in neurological diseases.