Morphine down regulates human vascular tissue estrogen receptor expression determined by real-time RT-PCR

Human vascular endothelial cells express the estrogen receptor-β (ER-β), which can be modulated by the opiate alkaloid morphine. Objectives: To determine if morphine is capable of down regulating the ER-β receptor in a similar fashion as the μ opiate receptor since they are both coupled to constitutive nitric oxide synthase derived nitric oxide release. Methods and Results: Endothelial cells obtain from human vascular tissues (saphenous vein, atria and primary saphenous vein cells) were treated with 1 uM morphine plus or minus the μ opiate receptor antagonist naloxone or CTOP (10 uM) for 24 h at 37°C. Total RNA was isolated from treated and untreated primary endothelial cells, and specific primers and a probe were used to determine the ER-β gene expression by real-time RT-PCR. Cells treated with morphine exhibited a down-regulation of ER-β, whereas nalox-one and CTOP were able to partially block the morphine effect. In addition, the 266 bp fragment generated by RT-PCR using the same primers as in the real-time PCR was sequenced and revealed a 100% sequence identity as the authentic ER-β gene sequence. Conclusions: These results indicate that ER-β is expressed in human vascular endothelial cells, and morphine appears to regulate this receptor in a similar fashion as the μ opiate receptor.