Genomic analysis of [d-Ala2, d-Leu5] enkephalin preconditioning in cortical neuron and glial cell injury after oxygen deprivation

Abstract

[d-Ala2, d-Leu5] enkephalin (DADLE) is a synthetic δ-opioid agonist that induces hibernation and promotes survival of neurons and glial cells in the central nervous system. Several mechanisms for the attenuation of hypoxic injury have been suggested, including control of intracellular signaling pathways via the δ-opioid receptor (DOR). However, the cellular and molecular mechanisms of DADLE in hypoxic injury are largely unknown. To investigate neuronal injury after oxygen-deprivation (OD) and DOR stimulation by DADLE, we used a lactate dehydrogenase assay, MTT assay, and immunofluorescence live/dead staining. And we used cDNA microarrays to investigate the influence of DADLE exposure on transcription after OD in rat cortical glial and neuronal co-culture. DADLE reduced neuronal injury after 24 h of OD. Preconditioning with DADLE before 24 h hypoxia exposure also altered gene expression in comparison with 24h OD without pretreatment. After DADLE exposure and hypoxia, 1917 of 39,511 genes (4.9%) were significantly induced or repressed at least 2.5-fold. Assigning differentially expressed ESTs (expressed sequence tags) to molecular functional groups revealed that DADLE affected many pathways including apoptosis, intracellular ion homeostasis, molecular chaperones, and glucose metabolism. We observed a coordinated change in expression of many genes (increased expression of potentially protective genes and decreased expression of potentially harmful genes) after DADLE exposure. A comprehensive list of regulated genes should prove valuable in advancing our understanding of the neuroprotective mechanisms of DADLE under OD.