咪唑啉受体及其对阿片药理作用的调节机制

用稳定转染咪唑啉1型受体(I1R)的细胞(CHO-I1),对I1R信号转导途径进行了初步研究。首次直接证实I1R的信号转导途径与活化PC-PLC继而产生DAG,其后引起丝裂原激活蛋白激酶(MAPK)酶促级联反应过程有关。采用共同稳定表达μ阿片受体(MOR)和I1R的CHO细胞表达系统(CHO-μ/I1细胞),对I1R在受体后水平抑制吗啡依赖的可能分子机制进行了研究。首次提供了胍丁胺通过作用于I1R而抑制吗啡依赖的直接实验证据,其分子机制可能主要是胍丁胺激活I1R抑制吗啡慢性处理时cAMP通路和Ca2+信号通路代偿性适应而抑制吗啡依赖的形成。     

利用RNA干扰技术研究I1咪唑啉受体在阿片依赖中的作用

目的：我们和国外实验室先后研究发现胍丁胺对阿片依赖具有调节作用，其作用可能与I1咪唑啉受体（I1-imidazoline receptor，I1R）有关。但由于没有特异性咪唑啉受体拮抗剂且胍丁胺的作用靶点较多，到目前为止，I1R是否为胍丁胺抗阿片依赖的主要作用靶点尚不能完全确定。因此，本文旨在利用RNA干扰技术确定I1R是否介导胍丁按对阿片依赖的调节作用。方法：利用RNA干扰技术下调细胞内源性I1R的表达，     

胍丁胺调节阿片功能的分子和神经生物学机制

胍丁胺是一种内源性生物活性物质,由左旋精氨酸在左旋精氨酸脱羧酶作用下脱羧生成。我们的前期研究发现不管是内源性还是外源性胍丁胺都具有明确的阿片功能调节作用,表现为镇痛、增强吗啡镇痛、抑制吗啡耐受,躯体依赖和精神依赖。近年来,在这些工作的基础上,我们研究了胍丁胺调节阿片功能的分子和神经生物学机制。提出了胍丁胺调节阿片功能可能和激活咪唑啉受体有关这一假说。为了证明这一假说的客观性,本实验室首次建立了IRAS-Cho细胞稳定表达系统,通过观察IRAS的亚细胞定位、配体结合特性、生物学功能和信号转等证明了由美国科学家克隆的IRAS就是野生型I1咪唑啉受体。在此细胞模型上,我们首次证明胍丁胺调节阿片功能与激活I1咪唑啉受体相关。为了在神经元上,特别是在整体行为学实验模型上证明上述发现的存在,本实验室用RNA干涉技术在大鼠原代培养海马神经元和大鼠摇体实验模型上进一步证明胍丁胺调节阿片功能与激活I1咪唑啉受体相关。     

ABIN1对μ阿片受体活性的抑制作用

目的 A20结合的核因子抑制蛋白(ABIN1蛋白)是通过细菌双杂交技术筛选得到的与MOR羧基端(C-端)有相互作用的蛋白。本研究在确定ABIN1蛋白与μ阿片受体(MOR)相互作用的基础上,明确ABIN1对MOR受体激动活性及MOR激活后信号通路的影响。方法 (1)用GST-pull-down实验、免疫荧光细胞化学共定位及免疫共沉淀(Co-IP)实验验证ABIN1与MOR-C有无相互作用。(2)建立稳定转染ABIN1与MOR的CHO细胞株,用[3H]diprenorphine进行受体配体结合实验,观察ABIN1对MOR与配体结合力的影响。(3)用[35S]GTP-γS实验,观察ABIN1对MOR激动活性的影响。(4)通过SDS-PAGE电泳观察ABIN1对MOR激活后受体磷酸化及ERK/p-ERK水平的影响,通过cAMP含量测定确定ABIN1对DAMGO急性作用于MOR抑制cAMP作用的影响。结果 GST-pulldown实验在细胞外证明ABIN1与MOR-C有相互作用,免疫荧光细胞化学共定位实验表明ABIN1与MOR在胞膜存在共定位,Co-IP实验证明在细胞水平ABIN1与MOR有相互作用。[3H]diprenorphine受体配体结合实验表明ABIN1对MOR受体配体亲和力没有明显影响,[35S]GTP-γS实验证明ABIN1能够抑制激动剂对MOR的激动活性,EC50值显著增加(P<0.05)。量效曲线右移。ABIN1能够明显抑制DAMGO作用于MOR后对cAMP含量的降低作用(P<0.05),ABIN1明显抑制MOR的磷酸化(P<0.05),ABIN1对MOR激活后的p-ERK水平有明显的抑制作用(P<0.01),对ERK水平没有明显影响。结论 ABIN1与MOR相互作用后抑制MOR受体激动活性、MOR的磷酸化及受体后信号通路。     

胍丁胺对体外培养海马神经前体细胞增殖的影响及作用机制

目的前期证明胍丁胺(agmatine,Agm)作为一种新型神经递质具有抗抑郁作用,能够促进慢性应激小鼠海马神经元再生。本实验通过观察胍丁胺对体外培养海马神经前体细胞增殖的影响及作用机制,探讨其抗抑郁作用的细胞分子机制。方法培养扩增新生大鼠海马神经前体细胞,通过3H-TdR参入法和CCK-8试剂盒检测胍丁胺对其增殖的影响;培养体系内加入H89(PKA特异性抑制剂)或PD98059(MEK特异性抑制剂),观察这两种抑制剂对胍丁胺作用的影响。结果胍丁胺在0.1~10μmol·L-1浓度范围内,浓度依赖性地促进神经前体细胞的增殖,这种促增殖作用可以被H89(10μmol·L-1)和PD98059(10μmol·L-1)取消。结论胍丁胺可以促进体外培养的海马神经前体细胞增殖,此作用与cAMP-PKA-CREB通路和MEK-ERK-CREB通路相关。     

芍药苷通过激活腺苷A1和A2a受体促进低氧条件下EPO基因的表达

目的探讨芍药苷影响促红细胞生成素(EPO)表达的靶受体及其下游分子信号通路。方法以不同剂量(0.02、0.2、2、20μmol·L-1)芍药苷,以及PI-3K通路抑制剂(LY294002 30 μmol·L-1)、腺苷A2a受体拮抗剂(SCH582610.2μmol·L-1)、腺苷A1受体拮抗剂(DPCPX 10 μmol·L-1)和激动剂(CPA1μmol·L-1)处理HepG2细胞在低氧条件下培养,用RT-PCR和Western blot的方法检测促红细胞生成素(EPO)表达。结果常氧条件下芍药苷抑制EPO的表达,低氧时2μmol·L-1浓度的芍药苷能促进EPO基因的表达但对蛋白表达没有影响,SCH58261、DPCPX、LY294002能抑制芍药苷升高EPO mRNA的现象。结论芍药苷能通过同时激活A1和A2a受体,然后进一步激活PI-3K通路促进低氧条件下EPO基因的表达。     

CCK-8与内源性阿片系统在吗啡依赖中的相互作用

目的通过观察不同剂量的CCK-8对吗啡依赖SH-SY5Y细胞模型内源性阿片系统的影响,初步探讨CCK-8与内源性阿片系统在吗啡依赖过程的相互作用及其机制。方法建立吗啡慢性依赖SH-SY5Y细胞模型,应用放射配基结合技术观察μ阿片受体(MOR)结合特征,应用Real-Time PCR技术检测前脑啡肽原(PENK)、前阿黑皮质素原(POMC)基因的表达,并观察CCK-8对上述指标的影响。结果①10μmol·L-1吗啡作用于全反式维甲酸(RA)分化6d的SH-SY5Y细胞48h,成功建立了慢性吗啡依赖模型;②CCK-8可剂量依赖性地抑制MOR的结合,并且此抑制作用可被CCK1及CCK2受体拮抗剂(L-364,718,LY-288,513)翻转;③10-7、10-6mol·L-1CCK-8使PENK、POMC的表达较正常组分别增加(5.81±0.84)、(7.26±1.55)倍和(4.55±0.73)、(5.16±0.82)倍。吗啡依赖后,PENK、POMC表达较正常组下降(0.43±0.10)倍和(0.37±0.07)倍,10-8、10-7、10-6mol·L-1CCK-8使下调的PENK、POMC表达增加,PENK与正常组的相对表达值为(0.63±0.10)、(0.86±0.21)、(1.17±0.19),POMC与正常组的相对表达值为(0.46±0.10)、(0.60±0.11)、(0.96±0.11)。10-10、10-9mol·L-1CCK-8对PENK、POMC表达无影响。结论低剂量(10-10、10-9mol·L-1)CCK-8可通过激活CCK受体抑制MOR的结合力,对PENK、POMC的表达无影响;高剂量(10-8～10-6mol·L-1)的CCK-8可使PENK、POMC基因表达增加,促进内源性阿片肽的生成,并可改善吗啡依赖后内源性阿片系统的失衡。     

胍丁胺抗大鼠身体依赖作用与阿片受体的关系

目的··：观察胍丁胺抗大鼠身体依赖作用与阿片受体间的关系。方法··：本文实验采用大鼠身体依赖实验和放射配体结合实验两种方法进行。结果··：胍丁胺虽然能剂量依赖性地抑制纳洛酮催促所引起的吗啡依赖大鼠戒断反应,但对３Ｈ－纳洛酮与大鼠前脑阿片受体结合反应无抑制作用（无直接作用）,亦不能影响当身体依赖发生时阿片受体对配体的亲和力下降和受体数量下调等代偿性适应变化（无间接作用）。结论··：虽然胍丁胺能抑制阿片类药物身体依赖,但对阿片受体既无直接也无间接作用。     

μ阿片受体的内吞抑制吗啡耐受的形成

阿片类药物是至今最有效的镇痛药,但是长期应用会产生药物耐受,大大限制了其临床应用。μ阿片受体和特定的激动剂结合后会出现内吞。研究发现,μ阿片受体是否内吞与耐受的发生有密切关系;加强μ阿片受体的内吞能够抑制受体耐受。不同的激动剂导致μ阿片受体内吞的能力是不同的;其导致耐受的能力和导致内吞的能力呈负相关。激动剂越容易引起μ受体内吞,就越不容易产生吗啡耐受。内吞的作用在于能抑制过度刺激μ受体而导致的环腺苷酸(cyclicadenosine monophosphate,cAMP)等兴奋性信号通路的激活,而内吞的μ受体也会很快回到细胞膜上,恢复和阿片类药物结合后激活抑制性GTP结合蛋白的能力。因此,对受体的内吞和其后迁移过程展开研究,可能为慢性疼痛的治疗找到新的路径。     

激动α_(1B)-肾上腺素受体对DDT1 MF-2细胞生长的刺激作用及其途径

目的　研究激动α1B 肾上腺素受体 (α1B AR)对DDT1MF 2细胞生长的影响及其机制。方法　用3H-胸腺嘧啶参入法测定细胞的DNA合成速率 ;用流式细胞计测定细胞周期。结果　去甲肾上腺素 (NE ,0 1～ 1μmol·L-1)可刺激DDT1MF 2细胞DNA的合成。磷脂酶C抑制剂 (U7312 2 ,10 μmol·L-1)、Ca2 +/ATP酶抑制剂 (CPA ,10 μmol·L-1)、胞内Ca2 +络合剂 (BAPTA/AM ,10 μmol·L-1)、PKC抑制剂(RO 31 82 2 0 ,0 1μmol·L-1或calphostinC ,0 1μmol·L-1)、酪氨酸激酶抑制剂 (tyrphostinA2 5 ,10 μmol·L-1或genis tein ,10 μmol·L-1)、MEK1/ 2抑制剂 (PD 980 5 9,10 μmol·L-1)均可阻断NE刺激细胞DNA合成的作用。结论　激动α1B AR可刺激DDT1MF 2细胞增殖 ,其信号转导途径可能与PLC激活、Ca2 +释放、PKC、TK和ERKs的激活有关     

Effect of agmatine on DAMGO-induced mu-opioid receptor down-regulation and internalization via activation of IRAS, a candidate for imidazoline I(1) receptor

Agmatine, an endogenous ligand for imidazoline I(1) receptor, has previously been shown to prevent opioid tolerance in rats and mice, but the cellular mechanisms remain unknown. In the present study, the effects of agmatine activation on imidazoline I(1) receptor on the desensitization, down-regulation and internalization of micro opioid receptor were investigated. Two cell lines, CHO cells transfected micro opioid receptor (CHO-micro cells) and co-transfected micro opioid receptor and imidazoline I(1) receptor antisera-selected protein (IRAS) (CHO-micro/IRAS cells), were used. In both CHO-micro cells and CHO-micro/IRAS cells, agmatine (0.01-10 microM) did not affect the desensitization of micro opioid receptor induced by [d-Ala(2), N-Me-Phe(4),Gly(5)-ol]-enkephalin (DAMGO) (10 microM) treatment for 30 min. However, agmatine (0.1-100 nM) co-pretreatment with DAMGO (1 microM) for 12 h concentration-dependently inhibited DAMGO-induced down-regulation of micro opioid receptor in CHO-micro/IRAS cells, but not in CHO-micro cells. Efaroxan, the I(1)/alpha(2)-adrenoceptors mix antagonist, completely reversed the inhibitory effect of agmatine, suggesting the participation of imidazoline I(1) receptor. In addition, agmatine (1-100 nM) inhibited DAMGO-induced internalization of micro opioid receptor in CHO-micro/IRAS cells, which was reversed by efaroxan as well. While treatment with DAMGO (1 microM) or co-treatment with agmatine (1-100 nM) for 12 h failed to affect the mRNA level of micro opioid receptor. Taken together, these results indicate that the inhibitory effect of agmatine on tolerance in vitro might be related to attenuation of the internalization and down-regulation of micro opioid receptor via activation of imidazoline I(1) receptor.     

IRAS, a candidate for I1-imidazoline receptor, mediates inhibitory effect of agmatine on cellular morphine dependence

Agmatine, an endogenous ligand for the I1-imidazoline receptor, has previously been shown to prevent morphine dependence in rats and mice. To investigate the role of imidazoline receptor antisera-selected protein (IRAS), a strong candidate for I1R, in morphine dependence, two CHO cell lines were created, in which mu opioid receptor (MOR) was stably expressed alone (CHO-mu) or MOR and IRAS were stably co-expressed (CHO-mu/IRAS). After 48 h administration of morphine (10 microM), naloxone induced a cAMP overshoot in both cell lines, suggesting cellular morphine dependence had been produced. Agmatine (0.1-2.5 microM) concentration-dependently inhibited the naloxone-precipitated cAMP overshoot when co-pretreated with morphine in CHO-mu/IRAS, but not in CHO-mu. Agmatine at 5-100 microM also inhibited the cAMP overshoot in CHO/mu and CHO-mu/IRAS. Efaroxan, an I1R-preferential antagonist, completely blocked the effect of agmatine on the cAMP overshoot at 0.1-2.5 microM in CHO-mu/IRAS, while partially reversing the effects of agmatine at 5-100 microM. L-type calcium channel blocker nifedipine entirely mimicked the effects of agmatine at high concentrations on forskolin-stimulated cAMP formation in CHO-mu and naloxone-precipitated cAMP overshoot in morphine-pretreated CHO-mu. Therefore, IRAS, in the co-transfected CHO-mu/IRAS cell line, appears necessary for low concentrations of agmatine to cause attenuation of cellular morphine dependence. An additional effect of agmatine at higher concentrations seems to relate to both transfected IRAS and some naive elements in CHO cells, and L-type voltage-gated calcium channels are not ruled out. This study suggests that IRAS mediates agmatine's high affinity effects on cellular morphine dependence and may play a role in opioid dependence.     

Functional interactions between μ opioid and I1-imidazoline receptors

OBJECTIVE To study the role of I1-Imidazoline receptor(I1R) in opioid dependence.METHODS Subcellular location of μ opioid receptor(MOR) and IRAS was investigated by immunocytochemistry.The interaction between MOR and IRAS was studied by co-immunoprecipitation and fluorescence resonance energy transfer(FRET).Further more,whether the interactions between IRAS and MOR would affect the signaling and the adaptation of MOR was studied in the cells expressing MOR and IRAS.RESULTS We found that MOR and IRAS colocalized in the HEK293 cells transfected MOR and IRAS and in the neurons of the cerebral cortex and hippocampus.Coimmunoprecipitation and FRET assays showed that there were interactions between the IRAS and MOR.High concentration reductant DTT did not interrupt the interactions,suggesting that the interactions were not mediated by disulfide bond.Further more,we found that the interactions did not influence the expression and affinity of MOR,as well as the activation of G proteins,adenylate cyclase and extracellular signal-regulated kinase(ERK) phosphorylation coupled to MOR after stimulated by DAMGO.However,over-expression of IRAS could attenuate DAMGO-induced MOR desensitization and internalization,accelerate MOR resensitization in the cells co-expressing IRAS and MOR,which probably by increasing the rate of dephosphorylation and recycling of MOR.The molecular mechanisms for that were on studying.CONCLUSIONThese findings indicate I1R is an important molecular to modulate opioid functions,and provide the further evidence to support I1R as a new target for treating opioid addiction.     

Modulation of agmatine on calcium signal in morphine-dependent CHO cells by activation of IRAS, a candidate for imidazoline I1 receptor

The present study investigated the effects of agmatine action on imidazoline I1 receptor antisera-selected protein (IRAS), a candidate for imidazoline I1 receptor, on prolonged morphine-induced adaptations of calcium signal and long-lasting alterations in gene expression to further elucidate the role of IRAS in opioid dependence. Two cell lines, Chinese hamster ovary cells expressing mu opioid receptor alone (CHO-mu) and expressing mu opioid receptor and IRAS together (CHO-mu/IRAS), were used. After chronic treatment with morphine for 48 h, naloxone induced a significant elevation of intracellular calcium concentration ([Ca2+]i) in CHO-mu and CHO-mu/IRAS cells. Agmatine (0.01-3 microM) concentration-dependently inhibited the naloxone-precipitated [Ca2+]i elevation when co-pretreated with morphine in CHO-mu/IRAS, but not in CHO-mu. Efaroxan, an imidazoline I1 receptor-preferential antagonist, completely reversed the effect of agmatine in CHO-mu/IRAS. Agmatine (1-10 microM) administration after chronic morphine exposure for 48 h partially decreased the [Ca2+]i elevation in CHO-mu/IRAS which was entirely antagonized by efaroxan, but not in CHO-mu. In addition, agmatine (1 microM) co-pretreated with morphine attenuated the naloxone-precipitated increases of cAMP-responsive element binding protein and extracellular signal-regulated kinase 1/2 phosphorylations and c-Fos expression in CHO-mu/IRAS. These effects were blocked by efaroxan as well. Taken together, these results indicate that the agmatine-IRAS action system attenuates the up-regulations of Ca2+ signal and its downstream gene expression in morphine-dependent model in vitro, providing additional evidence to support the contribution of IRAS to opioid dependence.     

胍丁胺对新生大鼠海马神经前体细胞增殖的影响

目的探讨胍丁胺对大鼠海马神经前体细胞增殖的影响及可能的作用机制。方法分离新生24 h大鼠的海马组织,制成单细胞悬液后进行无血清条件培养;用CCK-8试剂盒和3H-胸腺嘧啶核苷参入法检测细胞增殖和胍丁胺的作用。结果从新生大鼠海马分离得到的细胞可以持续分裂增殖形成细胞克隆(神经球);胍丁胺1、10μmol.L-1可以显著促进神经前体细胞的增殖,并且这种促增殖作用可以被依法克生所抑制。结论胍丁胺可以促进体外培养的新生大鼠海马神经前体细胞的增殖,其促增殖作用可能与咪唑啉Ⅰ(I1)受体有关。     

Agonist-selective mechanisms of mu-opioid receptor desensitization in human embryonic kidney 293 cells

The ability of two opioid agonists, [d-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin (DAMGO) and morphine, to induce mu-opioid receptor (MOR) phosphorylation, desensitization, and internalization was examined in human embryonic kidney (HEK) 293 cells expressing rat MOR1 as well G protein-coupled inwardly rectifying potassium channel (GIRK) channel subunits. Both DAMGO and morphine activated GIRK currents, but the maximum response to DAMGO was greater than that of morphine, indicating that morphine is a partial agonist. The responses to DAMGO and morphine desensitized rapidly in the presence of either drug. Expression of a dominant negative mutant G protein-coupled receptor kinase 2 (GRK2), GRK2-K220R, markedly attenuated the DAMGO-induced desensitization of MOR1, but it had no effect on morphine-induced MOR1 desensitization. In contrast, inhibition of protein kinase C (PKC) either by the PKC inhibitory peptide PKC (19-31) or staurosporine reduced MOR1 desensitization by morphine but not that induced by DAMGO. Morphine and DAMGO enhanced MOR1 phosphorylation over basal. The PKC inhibitor bisindolylmaleimide 1 (GF109203X) inhibited MOR1 phosphorylation under basal conditions and in the presence of morphine, but it did not inhibit DAMGO-induced phosphorylation. DAMGO induced arrestin-2 translocation to the plasma membrane and considerable MOR1 internalization, whereas morphine did not induce arrestin-2 translocation and induced very little MOR1 internalization. Thus, DAMGO and morphine each induce desensitization of MOR1 signaling in HEK293 cells but by different molecular mechanisms; DAMGO-induced desensitization is GRK2-dependent, whereas morphine-induced desensitization is in part PKC-dependent. MORs desensitized by DAMGO activation are then readily internalized by an arrestin-dependent mechanism, whereas those desensitized by morphine are not. These data suggest that opioid agonists induce different conformations of the MOR that are susceptible to different desensitizing and internalization processes.     

胍丁胺对炎性疼痛的镇痛作用及对吗啡镇痛作用的影响

目的观察胍丁胺对炎性疼痛的镇痛作用及其对吗啡镇痛作用的影响,研究胍丁胺的镇痛作用是否与激动咪唑啉受体或影响受体前谷氨酸和γ-氨基丁酸(gamma-aminobutyr-icacid,GABA)释放有关。方法应用福尔马林致大鼠炎性疼痛模型,观察胍丁胺镇痛和增强吗啡镇痛的作用。应用高效液相色谱技术测定胍丁胺对脊髓切片孵育液中谷氨酸和GABA基础释放量及对高钾诱发神经元去极化引起神经递质释放的影响。结果单侧足底注射5%福尔马林使大鼠出现明显的双相伤害性行为反应。胍丁胺抑制福尔马林引起的第二相疼痛行为反应及痛觉过敏,并增强吗啡对第二相疼痛的镇痛作用,但在第一相疼痛过程中,无明显镇痛和增强吗啡镇痛的作用。咪唑啉受体拮抗剂咪唑克生不能拮抗胍丁胺镇痛及增强吗啡镇痛的作用。1~1000μmol.L-1胍丁胺对脊髓谷氨酸和GABA的基础释放量和高钾诱发谷氨酸和GABA释放量的升高均没有影响。结论胍丁胺对炎性疼痛具有明确的镇痛作用,并明显增强吗啡的镇痛效果,其镇痛机制可能与咪唑啉受体无关,也不是通过在受体前水平抑制谷氨酸或促进GABA释放来实现的。