title: Melatonin protects SHSY5Y neuronal cells but not cultured astrocytes from ischemia due to oxygen and glucose deprivation.
abstract: As a potent free radical scavenger and antioxidant, melatonin protects brain tissue against ischemia-reperfusion injury, partly via suppression of ischemia-induced production of nitric oxide, when given before ischemia-reperfusion or within 2 hr of onset of ischemia. In this study, we examined the neuroprotective effect of melatonin in an in vitro model of ischemia. Primary cultured astrocytes were subjected to 4 or 8 hr of oxygen-glucose deprivation (OGD), and cultured SHSY5Y human neuronal cells were exposed to 1 hr of OGD. Melatonin was added to the medium at the commencement of OGD to achieve different final concentrations, and cell death was quantified using the measurement of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) at 24 hr after reversion of OGD. Treatment with melatonin did not affect the astrocytic cell death following 4 or 8 hr of OGD. The relative MTT values of the neuronal cells were (as mean +/- S.E.M.) 59.1 +/- 2.4% in the vehicle-treated OGD group and 80.1 +/- 2.7%, 82.5 +/- 2.9%, 74.1 +/- 2.3%, 64.2 +/- 2.3%, 62.7 +/- 2.8%, and 61.0 +/- 3.9% in the OGD groups treated with melatonin at 10(-3), 10(-4), 10(-5), 10(-6), 10(-7), and 10(-8) m, respectively. Reduction in cell death was significant following treatment with melatonin at 10(-3), 10(-4), or 10(-5) m. Reverse transcription-polymerase chain reaction showed that human mt1 and MT2 membrane receptors were not expressed in the cultured neuronal cells. Our results show that melatonin co-treatment protects cultured neuronal cells but not astrocytes against OGD-induced cell death in a dose-dependent manner and that the neuroprotection is independent of its known membrane receptors.
authors.affiliation: Division of Neurology, University Department of Medicine, Faculty of Medicine, Queen Mary Hospital, The University of Hong Kong, Pokfulam, Hong Kong. rtcheung@hkucc.hku.hk
authors.forename: Zhong
authors.initials: Z
authors.lastname: Pei
authors.forename: Raymond Tak Fai
authors.initials: RT
authors.lastname: Cheung
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects* / Q000473:pathology; D016923:Cell Death / Q000187:drug effects; D015687:Cell Hypoxia / Q000187:drug effects*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005947:Glucose / Q000172:deficiency; D006801:Humans; D007511:Ischemia; D008550:Melatonin / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects* / Q000473:pathology; D018696:Neuroprotective Agents / Q000494:pharmacology*; D051381:Rats; D011956:Receptors, Cell Surface / Q000096:biosynthesis; D018160:Receptors, Cytoplasmic and Nuclear / Q000096:biosynthesis; D044094:Receptors, Melatonin; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D018696:Neuroprotective Agents; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D044094:Receptors, Melatonin; D005947:Glucose; D008550:Melatonin