Effects of carbachol on apoptosis in human chronic myelogenous leukemic K562 cell line

Objectives: Muscarinic receptors mediate diverse actions of acetylcholine in the central nervous system and in non-nervous tissues innervated by the parasympathetic nervous system. Our study aims to evaluate the potential association of the M-3 muscarinic receptor with K562 cell proliferation and death. Materials and Methods: Cell proliferation was evaluated by bromodeoxyuridine (BrDU) incorporation. To show early, late apoptosis and cell death, cells were labelled with Annexin V, propidium iodide (PI) and analyzed by flow cytometry. Nuclear extracellular signal-regulated kinase (ERK/pERK) expression was measured by western blot analysis. Results: Treatment with carbachol (CCh) for 48h decreased cell number. Exposing K562 cells to CCh for 24h decreased the number of early apoptotic cells but did not change the number of late apoptotic and necrotic cells. CCh treatment for 48h increased the number of necrotic cells, but decreased the number of early and late apoptotic cells. In response to CCh, nuclear ERK expression was increased and this effect was reversed by 1,1-dimethyl-4-diphenylacetoxypiperidinium iodide (4DAMP). Nuclear pERK expression was decreased in CCh treated cells, 4DAMP did not reverse the effect. Conclusion: Our data suggest that cholinergic agonist CCh affects cell proliferation in K562 cells not only through muscarinic receptors but also through other cholinergic receptors.