Delta opioid agonist [D-Ala2, D-Leu5] enkephalin (DADLE) reduced oxygen–glucose deprivation caused neuronal injury through the MAPK pathway

Abstract

It has been demonstrated that [D-Ala2, D-Leu5] enkephalin (DADLE), a delta opioid agonist, protected neuron from hypoxic neuronal injury by activating the delta opioid receptor (DOR). However, whether DADLE can prevent neuronal injury induced by severe hypoxia like oxygen–glucose deprivation (OGD) is not clear. Here, we investigated whether DADLE has a protective effect against neuronal injury induced by oxygen–glucose deprivation. Neuron viability was measured by MTT and neuron injury was assessed by lactate dehydrogenase (LDH) release. Protein expression was examined by Western blot. The results showed that DADLE protected the cortical neuron in a dose-dependent way from OGD injury. And this neuroprotective effect could be completely blocked by delta2 opioid antagonist Naltrindole. DADLE increased phosphorylation of ERK and prevented OGD-induced p38 phosphorylation. Neither DADLE nor Naltrindole had any appreciable effect on phosphorylation of JNK. One of the protective mechanisms of DADLE on OGD neurons may be due to the dynamic balance between the activation of ERK and the p38.