Recent advances on the δ opioid receptor: from trafficking to function

Within the opioid family of receptors, δ (DOPrs) and μ opioid receptors (MOPrs) are typical GPCRs that activate canonical second-messenger signalling cascades to influence diverse cellular functions in neuronal and non-neuronal cell types. These receptors activate well-known pathways to influence ion channel function and pathways such as the map kinase cascade, AC and PI3K. In addition new information regarding opioid receptor-interacting proteins, downstream signalling pathways and resultant functional effects has recently come to light. In this review, we will examine these novel findings focusing on the DOPr and, in doing so, will contrast and compare DOPrs with MOPrs in terms of differences and similarities in function, signalling pathways, distribution and interactions. We will also discuss and clarify issues that have recently surfaced regarding the expression and function of DOPrs in different cell types and analgesia.

LINKED ARTICLES

This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2     

Pro-migratory actions of the prostacyclin receptor in human breast cancer cells that over-express cyclooxygenase-2

Metastasis is the major cause of death in cancer patients. Elevated expression of cyclooxygenase-2 (COX-2) is observed in many human cancers and over-production of downstream prostaglandins (PGs) has been shown to stimulate metastasis. A role for increased PGE₂ production has been proposed, but whether other PGs contribute is currently unclear. In this study the pro-migratory actions of individual PGs were evaluated in MDA-MB-468 breast cancer cells that stably over-expressed COX-2 (MDA-COX-2 cells); cell migration was quantified using 3D-matrigel droplet assays. Inhibition of the prostacyclin and PGE synthases, but not alternate prostanoid synthases, prevented the increase in MDA-COX-2 cell migration produced by arachidonic acid (AA); direct treatment of cells with the stable prostacyclin analogue cicaprost also promoted migration. Pharmacological antagonism and knockdown of the IP receptor decreased cell migration, while antagonists of the alternate DP, EP2, FP, and TP prostanoid receptors were inactive. In support of these findings, activation of the IP receptor also enhanced migration in the MDA-MB-468, MDA-MB-231 and A549 cell lines, and IP receptor knock-down in MDA-COX-2 cells decreased the expression of a number of pro-migratory genes. In further studies, the prostacyclin/IP receptor and PGE₂/EP4 receptor pathways were found to be functionally independent and the inhibition of phosphatidylinositol 3-kinase (PI3K) and p38 mitogen-activated protein kinase (MAPK) selectively impaired the IP-receptor-dependent migration in MDA-COX-2 cells. Taken together, the prostacyclin/IP/PI3K-p38 MAPK axis has emerged as a novel pro-migratory pathway in breast cancer cells that over-express COX-2. This information could be utilized in novel treatment strategies to minimize tumor metastasis.     

基于报告基因检测的PXR、FXR和LXRα激动剂高通量筛选模型的建立

目的建立基于报告基因法的高通量筛选细胞模型,用来发现PXR、FXR和LXRα受体激动剂。方法利用Real-time定量PCR方法比较HEK293、Hep G2和LS174T细胞中内源性核受体PXR、FXR和LXRα的表达量,将p SG5-h PXR和p GL3-XREM-CYP3A4、p EGFP-N3-h FXR和EcRETK-Luc、p CMX-FLAG-h LXRα和p GL3-XREM-CYP3A4等质粒分别共转染到工具细胞中,优化共转染比例,并考察阳性药与萤光素酶报告基因表达强度的量效关系、模型特异性和稳定性。结果 1根据Real-time定量PCR结果,模型选用低表达PXR、FXR和LXRα的HEK293细胞作为工具细胞;2根据不同共转染比例对报告基因活性的结果,PXR、FXR和LXRα报告基因药物筛选模型的报告基因和过表达质粒比例,最终分别选择1∶1、2∶1和2∶1;3模型中,报告基因活性均与相应阳性药物(PXR/Rif、FXR/CDCA和LXRα/T0901317)呈剂量依赖性增长;4仅PXR激动剂Rif、FXR激动剂CDCA和LXRα激动剂T0901317可分别明显增加相应筛选模型的报告基因活性,分别重复5次试验后,计算得Z'值分别为0.58、0.66和0.63。结论该研究建立的PXR、FXR和LXRα激动剂高通量筛选模型,具有良好的特异性和稳定性,适用于对PXR、FXR和LXRα受体激动剂的筛选,进而开发以核受体作为药物靶点的药物。     

血管紧张素Ⅱ对足细胞Notch通路及Nephrin表达的影响

目的探讨血管紧张素Ⅱ(AngⅡ)刺激小鼠足细胞对Notch通路、Nephrin表达的影响。方法 AngⅡ刺激小鼠足细胞并给予缬沙坦干预,采用免疫荧光化学、Western blot、Real-time PCR方法检测Notch1、Notch胞内域1(NICD1)、Hes1、Nephrin的表达情况。结果 AngⅡ呈时间依赖性增加足细胞Notch1、NICD1、Hes1表达,抑制Nephrin表达(P<0.01);缬沙坦可抑制AngⅡ对Notch通路的活化,增加Nephrin的表达(P<0.01)。结论 AngⅡ通过激活Notch通路降低足细胞Nephrin表达。     

脑室给予不同剂量的Capsazepine对LPS致大鼠发热过程的影响

目的在大鼠侧脑室内给予不同剂量的瞬时受体电位香草酸受体1(transient receptor potential vanilloid 1,TRPV1)拮抗剂Capsazepine,观察对LPS致热过程的影响。方法在侧脑室内预先给与3种剂量Capsazepine,随之腹腔给与LPS致热。在腹腔内埋植发射子遥测体温变化过程,同时应用荧光测定法检测下丘脑细胞内钙离子浓度的变化,Western blot方法检测TRPV1表达水平。结果随着Capsazepine剂量增大,LPS致大鼠发热水平升高,下丘脑细胞内钙离子浓度减少,TRPV1表达水平降低。结论 Capsazepine作用于大鼠下丘脑,可使LPS诱导的发热水平提高,此效应可能与TRPV1的作用有关。     

地佐环平对短暂电击所致创伤后应激障碍模型小鼠行为的影响

目的研究N-甲基-D-天冬氨酸(NMDA)受体非竞争性拮抗剂地佐环平(MK-801)对短暂电击所致创伤后应激障碍(PTSD)模型小鼠行为学的影响,探讨NMDA受体拮抗剂在PTSD治疗中应用的可能性。方法 1 ICR小鼠ip给予MK-801 0.0125,0.025,0.05和0.1 mg·kg-1,5和10 d后进行自发活动测试,观察小鼠自发活动。2连续2 d给予ICR小鼠不可逃避的足底电击(每天15次,0.8 m A,间隔10 s,持续10 s)制备PTSD模型。第1天电击后5 min,ip给予MK-801 0.0125,0.025和0.05 mg·kg-1或ig给予盐酸舍曲林15 mg·kg-1,每天1次,连续16 d。其中第3,8和15天测定僵住时间;第9天进行自发活动实验,观察水平跨越次数和垂直站立次数;第13天进行高架十字迷宫实验,观察进入开臂的次数和在开臂的滞留时间;第16天进行爬梯实验,观察爬梯数和站立次数。结果 1 MK-801 0.1 mg·kg-1连续给药5或10 d可显著抑制小鼠自发活动(P<0.01),其他各给药组对小鼠自发活动无显著影响。2与正常对照组比较,电击组、MK-801各剂量组及舍曲林给药组小鼠的水平跨越格数和垂直站立次数均无显著性差异;与正常对照组小鼠相比,电击组小鼠的僵住时间显著增加(P<0.01);小鼠进入开臂的次数和在开臂滞留时间的百分比显著减少(P<0.01);爬梯实验中小鼠的站立次数显著增加(P<0.01),提示模型建立成功。电击后小鼠的PTSD样行为学变化可以被伴随给予舍曲林15 mg·kg-1逆转,但MK-801无法逆转电击后小鼠的PTSD样行为。结论在不影响小鼠自发活动的剂量范围内,MK-801在小鼠短暂电击模型上无抗PTSD的行为学效应,单纯拮抗NMDA受体未必能发挥抗PTSD作用,这可能与PTSD发病机制的复杂性和NMDA受体结构与功能的复杂性有关。     

苦味受体抑制剂研究进展

自然界存在多种苦味物质,绝大多数苦味物质通过激活苦味受体而产生苦味.苦味受体抑制剂通过与苦味物质竞争结合位点而起到抑制苦味的作用,在食品和药物掩味方面发挥着重要作用.本文综述了苦味受体抑制剂的生理活性及其在药物中的应用,并根据其化学结构进行了分类.