title: Antiapoptotic and cytotoxic properties of delta opioid peptide [D-Ala(2),D-Leu(5)]enkephalin in PC12 cells.
abstract: The delta opioid peptide [D-Ala(2),D-Leu(5)]enkephalin (DADLE) has been shown to promote organ survival and to protect against methamphetamine-induced neurodegeneration. However, the cellular mechanisms of these actions of DADLE are not totally clear. We examined the action of DADLE in serum-deprived pheochromocytoma cells (PC12) and found that DADLE protected against cell death in those cells. However, the dose-response curves of the protective effects of DADLE are U-shaped as judged by three biochemical or morphological assays: the LDH release, the DNA laddering, and the apoptotic nuclei. It was found that femtomolar to picomolar concentrations of DADLE are antiapoptotic, whereas micormolar concentrations of DADLE are cytotoxic in PC12 cells. The protective effect of DADLE could be attenuated by a selective delta2 opioid antagonist and the cytotoxic action of DADLE was reduced by a selective mu opioid receptor antagonist. The treatment of cells with PD98059, a selective inhibitor of ERK kinase (MEK), or the transfection of cells with a dominant interfering form of MEK (MEK-KA97) blocked both the protective effect of DADLE and the ERK phosphorylation induced by DADLE. Cytotoxic concentrations of DADLE, on the other hand, caused an increase of Fas-ligand (FasL) in PC12 cells that was attenuated by a selective mu antagonist. Our results suggest, therefore, that endogenous opioid peptides may, at low concentrations, promote cell survival via the MEK-ERK pathway perhaps through delta2 opioid receptors, whereas they may kill cells at high concentrations via the activation of FasL through an as-yet unknown mechanism involving mu opioid receptors.
authors.affiliation: Cellular Pathobiology Unit, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland 21224, USA.
authors.forename: Teruo
authors.initials: T
authors.lastname: Hayashi
authors.forename: Li-I
authors.initials: LI
authors.lastname: Tsao
authors.forename: Tsung-Ping
authors.initials: TP
authors.lastname: Su
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002490:Central Nervous System / Q000187:drug effects* / Q000378:metabolism; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D003603:Cytotoxins / Q000494:pharmacology*; D053938:DNA Fragmentation / Q000187:drug effects / Q000502:physiology; D004277:DNA, Single-Stranded / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D016308:Enkephalin, Leucine-2-Alanine / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D053222:Fas Ligand Protein; D005822:Genetic Vectors; D007150:Immunohistochemistry; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000187:drug effects / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009292:Narcotic Antagonists / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D018696:Neuroprotective Agents / Q000494:pharmacology*; D016716:PC12 Cells; D051381:Rats; D011957:Receptors, Opioid / Q000378:metabolism; D014162:Transfection; D019014:fas Receptor / Q000187:drug effects / Q000378:metabolism
chemical_list: D016895:Culture Media, Serum-Free; D003603:Cytotoxins; D004277:DNA, Single-Stranded; D004791:Enzyme Inhibitors; D053222:Fas Ligand Protein; C505662:Faslg protein, rat; D008562:Membrane Glycoproteins; D009292:Narcotic Antagonists; D018696:Neuroprotective Agents; D011957:Receptors, Opioid; D019014:fas Receptor; D016308:Enkephalin, Leucine-2-Alanine; D007770:L-Lactate Dehydrogenase; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases