Calcium signaling and c-fos gene expression via mg muscarinic acetylcholine receptors in human T- and B-cells

We previously showed that blood acetylcholine (ACh) originates mainly from T-lymphocytes, and that stimulation of muscarinic ACh receptors (mAChRs) induces Ca2+ oscillations and up-regulates c-fos gene expression in both T- and B-lymphocytes. In the present study, we investigated which mAChR subtypes are involved in Ca2+ signaling and c-fos gene expression in human T- (CEM) and B- (Daudi) cells. Stimulation of mAChRs with 100 muM oxotremorine-M, an M-1/M-3 agonist, increased levels of intracellular free Ca2+ ([Ca2+](i)) and c-fos mRNA expression in both cell lines. 4-DAMP, an M-3 antagonist, more effectively blocked the oxotremorine-M-induced increase in [Ca2+](i) than pirenzepine and telenzepine, M-1-receptor antagonists; AF-DX 116, an M-2 antagonist; hexahydrosiladifenidol, a weak M-3 antagonist; or hexamethonium and d-tubocurarine, nicotinic receptor antagonists. McN-A-343 (100 muM), a partial M-1-receptor agonist, had no apparent effect on [Ca2+](i) in either cell line. The oxotremorine-M-induced up-regulation of c-fos transcription was inhibited by 4-DAMP, but not by pirenzepine or AF-DX 116. Our findings thus suggest that ACh released from T-lymphocytes acts as an autocrine/paracrine factor, transmitting a Ca2+-dependent signal to the nuclei of T- and B-lymphocytes via M-3 receptors.