Morphine and endomorphins differentially regulate micro-opioid receptor mRNA in SHSY-5Y human neuroblastoma cells.
A sensitive quantitative-competitive reverse transcriptase-polymerase chain reaction method was developed to measure micro-opioid receptor (MOR) mRNA expression in SHSY-5Y neuroblastoma cells. Differentiation of SHSY-5Y cells with either retinoic acid (RA) or 12-o-tetradecanoyl-phorbol-13-acetate (TPA) significantly increased MOR mRNA levels. Morphine treatment (10 microM) for 24 h decreased MOR mRNA levels in control, as well as RA- and TPA-differentiated cells. In contrast, chronic exposure to the opioid peptides endomorphin-1 or endomorphin-2 significantly increased MOR mRNA levels in undifferentiated and RA-differentiated cells. An opioid antagonist, naloxone, reversed the morphine and endomorphin-1 and -2 effects on MOR mRNA levels in undifferentiated SHSY-5Y cells, but naloxone had differential reversing effects on the agonists' regulation of MOR mRNA in RA- or TPA-differentiated cells. To investigate whether the changes in MOR mRNA expression paralleled changes in MOR receptor function, intracellular cAMP accumulation in SHSY-5Y cells was measured. After chronic treatment with morphine, forskolin-induced cAMP levels in SHSY-5Y cells were significantly higher than those of untreated control cells. In contrast, forskolin-induced cAMP accumulation levels were lower in cells treated with endomorphin-1 or -2 than in untreated control cells. Together, our studies indicate that the opioid alkaloid morphine and the opioid peptides endomorphin-1 and -2 differentially regulate MOR mRNA expression and MOR function in SHSY-5Y cells.
Yu
Xin
X
Department of Biology, Seton Hall University, 400 South Orange Ave, South Orange, NJ 07079, USA.
Mao
Xin
X
Blake
Allan D
AD
Li
Wen Xin
WX
Chang
Sulie L
SL
D000701:Analgesics, Opioid / Q000494:pharmacology*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004347:Drug Interactions; D006801:Humans; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009447:Neuroblastoma / Q000473:pathology; D009842:Oligopeptides / Q000494:pharmacology*; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D017450:Receptors, Opioid, mu / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D009842:Oligopeptides; D012333:RNA, Messenger; D017450:Receptors, Opioid, mu; C105293:endomorphin 1; D005576:Colforsin; D009270:Naloxone; C105294:endomorphin 2; D009020:Morphine; D000242:Cyclic AMP