Muscarinic cholinoceptor activation by pilocarpine triggers apoptosis in human skin fibroblast cells

The aim of the present work was to examine the role of muscarinic acetylcholine receptors (mAChRs) on apoptosis in human skin fibroblast cells. Neonatal human skin fibroblast cultures were stimulated with pilocarpine in the presence or absence of specific antagonists. Pilocarpine stimulates apoptosis, total inositol phosphates (InsP) accumulation and nitric oxide synthase (NOS) activity. All these effects were inhibited by atropine, mustard hydrochloride (4‐DAMP) and pirenzepine, indicating that M₁ and M₃ mAChRs are implicated in pilocarpine action. Pilocarpine apoptotic action is accompanied by caspase‐3 and JNK activation. The intracellular pathway leading to pilocarpine‐induced biological effects involved phospholipase C, calcium/calmodulin and extracellular calcium as U‐73122, W‐7, verapamil, BAPTA and BAPTA‐AM blocked pilocarpine effects. L ‐NMMA, a NOS inhibitor, had no effect, indicating that the enzyme does not participate in the apoptosis phenomenon. These results may contribute to a better understanding of the modulatory role of the parasympathetic muscarinic system on the apoptotic human skin fibroblast process. J. Cell. Physiol. 222: 640–647, 2010. © 2009 Wiley‐Liss, Inc.