CONICET | Buscador de Institutos y Recursos Humanos

Acetylcholine (ACh) is the main brain neurotransmitter, it can be detected in the blood of several mammals including humans. ACh synthesis also occurs in non-neuronal cells, such as immune cells. Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels that are activated by ACh and mediated calcium (Ca2+) signals. nAChRs are pentameric transmembrane proteins, some are homomeric nAChRs, such as α7 and others are heteromeric nAChRs. In the present study, we investigated the expression of α7 in NK cells and the regulation of NK cell function by agonists and antagonist of α7 during their activation with IL-12, IL-18 and IL-15 for 48 h. First, we determined the surface expression of α7 with Alexa488-conjugated α-bungarotoxin (α-Bgt), a specific antagonist of α7. Strong binding of α-Bgt was observed on the surface of activated NK cells by confocal microscopy and flow cytometry, while it was slightly detected in non-activated cells. Using confocal microscopy and Fluo-3/AM, a Ca2+-sensitive fluorescent indicator, we observed a 1.5-2.5 fold increase of intracellular Ca2+ in activated NK cells when nicotine (an agonist of nAChRs) was added, indicating that α7 is functional in NK cells. We also observed that nicotine and PNU282987 (a specific agonist of α7) induced a down-regulation of the expression of NKG2D, and this effect was abolished by α-Bgt, without affecting other NK cell receptors such as NKp46. Moreover, NK cells stimulated with IL-12, IL-15 and IL-18 incubated with nicotine and PNU120596 (a specific allosteric modulator of α7) showed a reduction in the production of IFN-γ. Overall, our results provide evidence that effector function and phenotype of NK cells can be negatively regulated by activation of α7 receptor, which may contribute to tumor progression or dissemination of intracellular infections where NKG2D and IFN-γ play a critical role.