Ca2+ oscillation and c-fos gene expression induced via muscarinic acetylcholine receptor in human T- and B-cell lines.

We previously reported that blood acetylcholine (ACh) mainly originates from T-lymphocytes and that muscarinic (Ms) ACh receptor mRNA is expressed in both T- and B-lymphocytes. In the present study, we used confocal laser scanning microscopy and fluo-3, a calcium-sensitive indicator, to investigate the effects of Ms-ACh receptor agonists on the intracellular free Ca2+ concentration ([Ca2+]i) in single cells from human T-cell (CEM) and B-cell (Daudi) lines, which we used as models of lymphocytes. In both cell lines, stimulation of Ms-ACh receptors with ACh (0.1-100 microM), bethanechol (100 microM), car-bachol (100 microM) or oxotremorine-M (Oxo-M; 0.1-100 microM) induced [Ca2+]i-dependent increases in fluo-3 fluorescence, which in the presence of extracellular Ca2+ were followed by oscillations in [Ca2+]i that persisted for at least 10 min. All effects were completely blocked by atropine (1 microM), an Ms-ACh receptor antagonist. In both cell lines Oxo-M (100 microM) up-regulated expression of c-fos mRNA in an extracellular Ca2+-dependent manner. Again, the effect was blocked by 1 microM atropine. These results provide the first evidence that stimulation of Ms-ACh receptors induces Ca2+ oscillations and up-regulates c-fos gene expression in T- and B-lymphocytes, which is consistent with the notion that ACh released from T-lymphocytes triggers nuclear signaling via Ms-ACh receptors.