The MDM2-p53 signalling pathway is involved in neuronal ischemic tolerance

Resumen del póster presentado al XXXIX Congreso de la Sociedad Española de Bioquímica y Biología Molecular, celebrado en Salamanca del 5 al 8 de septiembre de 2016.Brain ischemic preconditioning (IPC) refers to a state of transient tolerance of the brain tissue to a lethal insult that can be evoked by a prior mild insult. It is thought that IPC may induce different pathways responsible for neuroprotection. These mechanisms can involve the attenuation of cell damage pathways including the apoptotic cell death. In this context, p53 is a stress sensor that accumulates during brain ischemia leading to neuronal death. The mouse double minute2 homolog (MDM2), a p53-specific E3 ubiquitin ligase, is the main cellular antagonist of p53, mediating its degradation by the proteasome. Increased levels of MDM2 inhibit p53 stability and inactivate apoptotic function, although the role of MDM2 in neuroprotection is largely unknown.Here, we study the role of MDM2 and p53 interaction on IPC-induced neuroprotection. Primary cortical neurons were exposed to a moderate subtoxic concentration of N-methyl-D-aspartate (NMDA; 20μM NMDA; IPC condition) for 2 hours, followed by incubation for further 90 min in normoxic (presence of oxygen and glucose) or ischemic (oxygen and glucose deprivation; OGD). In parallel, control neurons were not stimulated with NMDA. After 4 hours of incubation in culture medium (reoxygenation condition), neuronal apoptosis (Annexin-V-staining) was analyzed by flow cytometry. Gene expression and protein levels were determined by RT-qPCR and western blotting, respectively.Our results show that IPC induced the expression of MDM2 in neurons, leading to MDM2 accumulation at 4 hours after OGD. Moreover, IPC prevented OGD-induced p53 stabilization, caspase-3 activation and apoptosis, which were prevented by neuronal treatment with the MDM2 inhibitor nutlin-3. These finding demonstrate the key role of the MDM2-p53 signalling pathway in neuroprotection induced by IPC against a subsequent ischemic insult and poses MDM2 as an essential target in ischemic tolerance.This work was funded by grants from The Instituto de Salud Carlos III (Miguel Servet I CP0014/00010; RD12/0014/0007) and FEDER (European regional development funding).Peer reviewe