Propofol increases µ-opioid receptor expression in SH-SY5Y human neuroblastoma cells

The aim of the present study was to explore the effect of propofol, a intravenous sedative-hypnotic agent used widely in inducing and maintaining anesthesia, on µ-opioid receptor (MOR) expression in a human neuronal cell line. SH-SY5Y human neuroblastoma cells were treated with various concentrations of propofol (1, 5, 10 or 20 µM) for different lengths of time (6, 12 or 24 h). Real-time quantitative RT-PCR showed that at a concentration range of 1-10 µM, propofol increased MOR mRNA levels in a statistically significant dose- and time-dependent manner within 12 h of treatment. Western blot analyses demonstrated that propofol treatment for 12 h dose-dependently increased the MOR protein levels. In the 12-h SH-SY5Y-treated cells, propofol dose-dependently increased MOR density (Bmax) in the cell membranes. In addition, in the presence of the transcription inhibitor actinomycin D (1 mg/ml), propofol (10 µM) had no significant effect on the MOR mRNA levels over time. The results suggested that propofol dose- and time-dependently enhances MOR expression in SH-SY5Y human neuroblastoma cells at the transcriptional level, leading to an increased density of ligand-binding MORs in the cell membranes. This study demonstrated for the first time a link between propofol and the opioid system, thereby providing new insights into propofol mechanism of action and potential for abuse.