The octadecaneuropeptide ODN prevents 6-hydroxydopamine-induced apoptosis of cerebellar granule neurons through a PKC-MAPK-dependent pathway

摘要

Oxidative stress, induced by various neurodegenerative diseases, initiates a cascade of events leading to apoptosis, and thus plays a critical role in neuronal injury. In this study, we have investigated the potential neuroprotective effect of the octadecaneuropeptide (ODN) on 6-hydroxydopamine (6-OHDA)-induced oxidative stress and apoptosis in cerebellar granule neurons (CGN). ODN, which is produced by astrocytes, is an endogenous ligand for both central-type benzodiazepine receptors (CBR) and a metabotropic receptor. Incubation of neurons with subnanomolar concentrations of ODN (10-18 to 10-12 M) inhibited 6-OHDA-evoked cell death in a concentration-dependent manner. The effect of ODN on neuronal survival was abrogated by the metabotropic receptor antagonist, cyclo1-8[DLeu 5]OP, but not by a CBR antagonist. ODN stimulated polyphosphoinositide turnover and ERK phosphorylation in CGN. The protective effect of ODN against 6-OHDA toxicity involved the phospholipase C/ERK MAPK transduction cascade. 6-OHDA treatment induced an accumulation of reactive oxygen species, an increase of the expression of the pro-apoptotic gene Bax, a drop of the mitochondrial membrane potential and a stimulation of caspase-3 activity. Exposure of 6-OHDA-treated cells to ODN blocked all the deleterious effects of the toxin. Taken together, these data demonstrate for the first time that ODN is a neuroprotective agent that prevents 6-OHDA-induced oxidative stress and apoptotic cell death. We proposed the following cascade for the neuroprotective effect of octadecaneuropeptide (ODN) against 6-OHDA-induced neuronal death: ODN provokes a stimulation of ERK phosphorylation, through a PKC-dependent mechanism. Activation of ERK counteracts the inhibition of Bcl-2 and the stimulation of the pro-apoptotic gene Bax induced by reactive oxygen species (ROS) formation and glutathione (GSH) depletion. These data may allow the development of new strategies for cerebral injury treatment.