Protection from interferon--induced neuronal apoptosis through stimulation of muscarinic acetylcholine receptors coupled to ERK1/2 activation

Background and PurposeAlthough clinically useful for their immunomodulatory, antiproliferative and antiviral properties, type I interferons (IFNs) are involved in the pathogenesis of several neurodegenerative/neuroinflammatory diseases. In the present study, we investigated the ability of cholinergic stimulation to protect from IFN--induced neuronal apoptosis. Experimental ApproachThe effects of the ACh receptor agonist carbachol (CCh) on IFN--induced apoptosis of human SH-SY5Y neuroblastoma cells were examined by using western blots, immunofluorescence and cytofluorimetry. The involvement of muscarinic acetylcholine receptors (mAChRs) was assessed by using selective antagonists and siRNA transfection. Pharmacological inhibitors and overexpression of ERK2 and an ERK2 constitutively active form (ERK2-CA) were employed to study ERK1/2 signalling. The effects of oxotremorine-M (Oxo-M) on IFN--induced apoptosis of mouse hippocampal neurons were examined by measuring cleaved caspase 3 expression. Key ResultsIn SH-SY5Y cells, CCh inhibited IFN--induced mitochondrial cytochrome c release, activation of caspases 9, 7 and 3, PARP cleavage and DNA fragmentation. The anti-apoptotic effect of CCh was mediated by M-3 receptors, blocked by G(q/11) antagonist YM254890 and PKC inhibitor Go 6983, impaired by inhibition of ERK1/2 pathway, potentiated by overexpression of ERK2 and mimicked by ERK2-CA. Blockade of JNK activation enhanced the CCh anti-apoptotic response. IFN- inhibited JNK activation and up-regulated CCh-induced ERK1/2 signalling. In hippocampal neurons, Oxo-M reduced IFN--induced apoptosis; this effect was antagonized by blockade of M-1/M-3 receptors and ERK1/2. Conclusions and ImplicationsStimulation of mAChRs counteracted IFN--induced neuronal apoptosis through the activation of ERK1/2 signalling. The data indicate that activation of ERK1/2-coupled mAChRs may be an effective strategy for preventing IFNs neurotoxicity.