Espanol_2012_Eur.J.Pharmacol_683_43

The submandibular gland-derived tumor cell line SCA-9 is considered a useful tool to study the signaling pathways involved in proliferation, and their regulation, triggered by different stimuli. It is proposed that the non neuronal cholinergic system: acethylcholine, the enzymes that synthesize and degrade it, and the nicotinic and muscarinic receptors, play a key role in tumorigenesis. Here, we investigate the role of muscarinic receptors in SCA-9 cell proliferation, and the modulation of cholinergic signaling pathways exerted by the nuclear transcription factor kappaB (NF-kappaB). The activation of cholinergic receptors by carbachol (10(-)(9)M) increased cell proliferation (P<0.001). This was prevented by preincubating cells with the muscarinic antagonist atropine but not by mecamylamine, a nicotinic receptor blocker. Phospholipase C (PLC)/nitric oxide synthase (NOS)/arginase pathway is involved in this effect, since carbachol stimulated nitric oxide production, increased NOS2 and NOS3 expressions, urea production, and arginase II expression (P<0.001). Also, phospholipase A(2) (PLA(2))/cyclooxygenase (COX) pathway is up-regulated in carbachol-induced SCA-9 cell proliferation, because prostaglandin E(2) liberation (P<0.001) is increased and COX-1 expression is turned up (P<0.001). Interactions between PLC/NOS/arginases and PLA(2)/COX pathways via its metabolites were detected. SCA-9 cells exhibit a constitutive activation of NF-kappaB, which regulates carbachol-induced NOS2 and 3, arginase II and COX-1 expressions. In addition, protein kinase C is involved in the up-regulation of NOS2 and arginase II enzymes induced by carbachol via NF-kappaB. In conclusion, the activation of cholinergic receptors in SCA-9 tumor cells promotes proliferation via muscarinic effector enzymes, and reveals the participation of NF-kappaB at this step of tumorigenesis.