孤啡肽在癫痫中作用的研究进展

孤啡肽(nociceptin/orphanin FQ)是1995年发现的阿片受体样受体(opioid receptor like 1 receptor,ORL1 receptor)的内源性配体。孤啡肽和孤啡肽受体系统构成一种新的神经肽系统,具有多种生物学功能。越来越多的研究表明,孤啡肽通过调节神经递质(包括兴奋性神经递质和抑制性神经递质)的释放或传递而对癫痫起作用。本文就孤啡肽和孤啡肽受体的分布及生物学功能进行综述,重点阐述孤啡肽在癫痫中的作用的研究进展。     

孤啡肽受体信号转导及功能研究进展

孤啡肽受体是阿片受体的家族成员,属于G蛋白偶联受体中A类视紫红质样受体,其天然的内源性配体被称为痛敏肽。孤啡肽受体分布广泛,对神经系统疾病有着重要的作用。本文就孤啡肽配体-受体系统生物学作用做简单综述,从而为孤啡肽受体参与相关疾病的发病机制提供理论依据。     

PPARγ天然激动剂的研究进展

过氧化物酶体增殖剂活化受体γ(PPARγ)是一个由配体激活的核转录因子,属于核激素受体(nuclear hormone receptor)超家族.它与脂肪形成、免疫应答以及脂质和糖类代谢等生理过程极其相关.尽管PPARγ的合成激动剂已广泛应用于胰岛素致敏剂,但是PPARγ的天然激动剂的鉴定一直不是很清楚,目前,PPARγ的天然激动剂主要有氧化的脂肪酸和硝基脂肪酸,包括9-羟十八碳二烯醇(9-HODE),13-羟十八碳二烯醇(13-HODE),5-脱氧前列腺素J2,油酸和亚油酸的硝基衍生物(分别为OA-NO2和LNO2)等.本文综述了近年的PPARγ的天然激动剂的研究进展.     

螺环哌啶类似物作为DOR激动剂的特征结构研究

阿片受体激动剂与特定阿片受体亚型结合,常用来治疗与外伤、癌症或心脏病相关的严重疼痛,是十分有吸引力的药用物质．阿片受体有3种经典亚型(δ, κ, μ),均有与其对应的激动剂．δ阿片受体(DOR)激动剂因其还有明显的抗焦虑、抗抑郁和器官保护作用,是非常有前景的药物．本文研究了一批共102个N-取代螺环哌啶类似物作为δ阿片受体激动剂的分子,采用比较分子力场(CoMFA)和比较分子相似性指数(CoMSIA)两种分析方法对所有分子进行了三维定量构效关系(3D-QSAR)研究,其中基于疏水场和氢键供体场参数建立的CoMSIA模型最佳,其模型结果为：Q²=0.501,R²_ncv=0.787,R²_pre=0.780,证明模型自我吻合良好,同时有较强的内部及外部预测能力．而模型的等势线图分析表明,在R₁处引入疏水性的取代基及在R₂处引入亲水性的取代基或氢键供体基团对提高激动剂活性有利．这些结论有助于更好地理解N-取代螺环哌啶类似物作为DOR激动剂的机理,为新型的δ阿片受体激动剂的设计和优化提供一定的指导．     

神经肽S功能与构效关系研究进展

神经肽S (neuropeptide S,NPS) 是通过反向药理学策略鉴定的由20 个氨基酸组成的新神经肽,它激活G蛋白偶联受体(NPSR) 而发挥作用。NPS及其受体主要分布于中枢上与觉醒和应激相关的脑区。目前的研究表明NPS 系统具有广泛的生理作用,如增加觉醒、抑制睡眠、抗焦虑作用、抑制摄食和调节免疫功能等,成为相关疾病的一个重要的新药物靶点。同时,研究神经肽S 的构效关系并寻找新的高效激动剂和选择性拮抗剂,对揭示其作用机理有重要意义。     

孤啡肽受体对痛觉调控作用的研究进展

孤啡肽受体是继经典的mu阿片受体、kappa阿片受体和delta阿片受体之后发现的又一类新型阿片受体,不仅在结构上具有同上述阿片受体相类似的特征,而且可介导相同或相似的细胞内生物学反应.孤啡肽受体对痛觉反应具有独特的调控模式.一方面,在背根神经节以及脊髓水平,孤啡肽受体主要介导镇痛效应,并且在脊髓水平还与其他阿片受体有协同效应以增强镇痛效果.另一方面,在脊髓上水平,孤啡肽受体往往产生痛敏而拮抗了其他阿片受体的镇痛效应.此外孤啡肽受体对痛觉的调控在不同物种间也表现一定的差异性.这为进一步阐明内源性阿片系统的痛觉调控作用提供一定的理论依据.     

脂联素受体激动剂研究进展

脂联素是人和动物体内重要的内源性生物活性激素，具有改善胰岛素抵抗、调控脂类代谢、抗动脉粥样硬化、保护心脏、抗炎、抗氧化应激、抗纤维化以及调控细胞凋亡等作用。脂联素需要与其受体结合才能发挥生物学功能，但因其结构和浓度的影响，脂联素在临床上的应用受到一定程度限制。研究发现，多种脂联素受体激动剂通过激活脂联素受体发挥与脂联素相似的生物学功能，且脂联素受体激动剂多为人工合成的小分子或筛选的多肽，作用效果更加明确。本文整理了目前已经报道的脂联素受体激动剂及其研究进展，概述了脂联素受体激动剂对肝脏、肾脏、心脏、血管、眼和皮肤等相关器官或组织疾病的作用或影响，为开发以脂联素及其受体为靶点的治疗药物提供理论依据。     

阿片受体激动剂对猪冠状动脉肌条作用的研究

采用螺旋肌条生物检定技术研究阿片受体激动剂对猪冠状动脉肌条的影响。结果显示κ,μ,δ亚型选择性激动剂Ｕ－５０４８８Ｈ,羟甲基芬太尼,吗啡,Ｄ－ａｌａ－ＤＬｅｕ－ｅｎｋｅｐｈａｌｉｎ（ＤＡＤＬＥ）以及广谱激动剂依托啡都可以引起肌条的收缩,收缩强度以Ｕ－５０４８８Ｈ＞吗啡＞依托啡＞ＯＭＦ,ＤＡＤＬＥ。上述作用均呈量效关系,纳洛酮对上述各亚型激动剂的作用不仅不能拮抗,反有增强作用,纳洛酮本射亦有致收缩作     

M1胆碱受体选择性别构激动剂的虚拟筛选和体外活性研究

目的:M1毒蕈碱型乙酰胆碱受体(M1受体)在改善学习和记忆等高级认知功能障碍中起重要作用,本文利用计算机辅助药物设计和高表达各M受体亚型的CHO细胞(Chinese hamster ovary cell,中国仓鼠卵巢细胞),以期筛选获得新型M1受体选择性别构激动剂。方法:通过计算机辅助药物设计方法,对已知具有M1受体选择性作用别构激动剂与M1受体的晶体结构进行对接,确定活性对接口袋,据此进行化合物库虚拟筛选;利用高表达各M受体亚型的CHO细胞,对化合物进行体外活性检测。结果:虚拟筛选得到184个化合物,其中,体外实验显示化合物AJ-292和AG-205-6对M1受体有明显的激动效果,而对M3、M5受体则无影响。结论:综合利用虚拟筛选、结构分析以及特异性活性分析,筛选出具有M1受体高选择性激动作用的化合物AJ-292和AG-205-6,为设计开发新型的M1选择性别构激动剂奠定了基础。     

真有K受体亚型吗?

阿片肽有μ、δ、κ三种受体。其中κ受体的激动剂无成瘾和呼吸抑制作用,这给广泛使用吗啡类镇痛药物提供了一条有益的途径。由于κ激动剂也有自身的副作用,因此人们推测,是否能通过确定出κ受体亚型而寻找到一种无副作用的κ激动剂。κ亚型的存在最初是根据受体结合实验提出的。当μ、δ受点被自身特异的配体封闭以后,组织中仍能同非特异配体(对μ、δ、κ无特异选择性)结合的受点称κ受点。在豚鼠脊髓结合[H~3]-ethylketazocine(κ非特异配体)的实验中发现,存在对DADLE(脑腓肽类似物)敏感和不敏感两类κ受点。最近报道,组织对[H~-]-ethylketazocine呈现不同的亲和力:豚鼠脑以高亲和力κ受点为主,而大鼠脑则是以低亲和力κ受点为主。在寻找出κ受体的特异配体U-50488H和DynA(1-17)以后,发现这两种配体所结合的κ位点较非特异配体结合的κ位点要少,这可能间接地预示U-50488H和DynA(1-17)的结合位点是κ受体的某一个亚型。但至     

In Silico Study of the Structurally Similar ORL1 Receptor Agonist and Antagonist Pairs Reveal Possible Mechanism of Receptor Activation

An opioid receptor like (ORL1) receptor is a member of a family of G-protein coupled receptors. It is a new pharmaceutical target with broad therapeutic potential in the regulation of important biological functions such as nociception, mood disorders, drug abuse, learning or cardiovascular control. The crystal structure of this receptor in complex with an antagonist was determined recently (PDB ID: 4EA3). By removing the ligand and subjecting the empty receptor to molecular dynamics simulation in a solvated lipid membrane we obtained an optimized ORL1 receptor structure which could be used in a subsequent docking study of two structurally similar agonist–antagonist ligand pairs. Ligands were docked to the empty ORL1 receptor (with and without the third intracellular loop, IC3) in different orientations, and the resulting complexes were monitored during molecular dynamics simulation in order to see how the subtle differences in structure of agonists and antagonists might affect ligand–receptor interactions and trigger receptor activation. It was established that agonists and antagonists bound to the same, relatively large, binding site in the receptor, created by residues from transmembrane helices TM2, TM3, TM5, TM6 and TM7 and close to the extra cellular end of the receptor bundle. The key difference between these two types of ligands is interaction with residue Val283^6.55 and a flexibility of ligand molecules. Ligands that cannot easily avoid this interaction will initiate movement of the intracellular end of TM6 (by a mechanism which involves Met134^3.36 and several aminoacids of TM5) and possibly activate the receptor when assisted by G-protein.     

Co-expressions of different opioid receptor types differentially modulate their signaling via G(16)

Combinations of two different types of opioid receptors - delta-, kappa-, mu-opioid receptors (DOR, KOR, and MOR) and opioid receptor-like receptor 1 (ORL(1)) - were co-expressed with the alpha subunit of G(16) in COS-7 cells, and the ability of various selective agonists to induce activation of phospholipase Cbeta was examined. Nociceptin/orphanin FQ-induced response was enhanced when ORL(1) was co-expressed with MOR or KOR but not DOR. The kappa-agonist U50,488H induced a modest inositol phosphate formation when KOR was expressed alone or with MOR, but the response was attenuated when co-expressing with either DOR or ORL(1). It is suggested that the co-expressions of two different opioid receptor types indeed modify their downstream signaling events.     

Structural requirements of nociceptin antagonist Ac-RYYRIK-NH2 for receptor binding.

Ac-RYYRIK-NH2 is a peptide isolated from the peptide library as an antagonist that inhibits the biological activities of nociceptin, a hyperalgesic neuropeptide. In order to clarify the structural requirements of this peptide for binding to the nociceptin receptor ORL1, systematic structure-activity studies were carried out. The result of Ala-scanning indicated that the N-terminal tripeptide RYY(= Arg-Tyr-Tyr) is crucially important for binding to the ORL1 receptor. Residual truncations from the N- or C-terminus revealed the special importance of the N-terminal Arg residue. The removal of protecting groups indicated that the N-terminal acetyl group is essential, but the C-terminal amide group is insignificant. These results indicated the conspicuous importance of acetyl-Arg at position 1 of Ac-RYYRIK-NH2 as a key structure allowing binding to the receptor. To investigate the binding site of this peptide in the ORL1 receptor, we synthesized and assayed a series of analogues of the nociceptin dibasic repeat region, residues 8-13 of RKSARK. None of the derivatives were active. Ac-RYYRIK-NH2 was inactive for the mu opioid receptor to which nociceptin binds with considerable strength. All the results suggested that the mode of binding between Ac-RYYRIK-NH2 and the ORL1 receptor is different to that between the ORL1 receptor and nociceptin, and that it may consist of interaction with the receptor site to which nociceptin(1-7) or -(14-17) binds.     

Opioid receptor-like 1 (ORL1) receptor binding and the biological properties of Ac-Arg-Tyr-Tyr-Arg-Ile-Arg-NH2 and its analogs.

Hexapeptides such as Ac-Arg-Tyr-Tyr-Arg-Ile-Lys-NH(2) and Ac-Arg-Tyr-Tyr-Arg-Trp-Arg-NH(2) have been isolated from a combinatorial peptide library as small peptide ligands for the opioid peptide-like 1 (ORL1) receptor. To investigate the detailed structural requirements of hexapeptides, 25 analogs of these hexapeptides, based on the novel analog Ac-Arg-Tyr-Tyr-Arg-Ile-Arg-NH(2) (1), were synthesized and tested for their ORL1 receptor affinity and agonist/antagonist activity on mouse vas deferens (MVD) tissues. Analog 1 and its Cit(6)-analog (10) were found to possess high affinity to the ORL1 receptor, comparable to that of nociceptin/orphanin FQ, and exhibited potent antagonist activity (pA(2) values of 7.77 for 1 and 7.51 for 10, which are higher than that of [NPhe(1)]nociceptin(1-13)-NH(2) (6.90) on MVD assay. It was also found that the amino acid residue in position 5 plays a key role in agonist/antagonist activity, i.e. an L-configuration aliphatic amino acid is required for potent antagonist activity, while a nonchiral or D-configuration residue produces potent agonist activity. These lines of evidence may provide insight into the mechanisms controlling agonist/antagonist switching in the ORL1 receptor, and may also serve to help developing more potent ORL1 agonists and antagonists.     

Discovery of selective farnesoid X receptor agonists for the treatment of hyperlipidemia from traditional Chinese medicine based on virtual screening and in vitro validation

Abstract

Farnesoid X receptor (FXR), a bile acid receptor, has important roles in maintaining bile acid and cholesterol homeostasis, which is an attractive target for hyperlipidemia. Present study aimed to discover potential selective FXR agonists over G-protein coupled bile acid receptor 1 (GPBAR1, TGR5) from traditional Chinese medicine (TCM) by using virtual screening, in vitro studies and molecular dynamics simulation (MD). Ligand-based pharmacophore model for FXR was firstly built to screen FXR agonists from the Traditional Chinese Medicine Database (TCMD). Then, 21 FXR crystal structures were clustered in two types and two representative structures (PDB ID: 3OMM and 3P89) were, respectively, used to carry out molecular docking to refine the screened result. Moreover, the pharmacophore model for GPBAR1 was built to screen selective FXR agonists with no activity on GPBAR1. A set of 24 candidate selective FXR agonists which fitvalue of FXR pharmacophore model and docking score of 3OMM and 3P89 were in the top 100 and cannot match the pharmacophore model for GPBAR1 were obtained. By the lipid-lowering activity test in HepG2 cell lines, Arctigenin was identified to be potential selective FXR agonist with the activity of 20?μmol·L^?1. After down-regulating FXR, Arctigenin could increase the mRNA of FXR while exerted no effect on the mRNA of GPBAR1. MD was further used to interpret the mechanism of Arctigenin with the representative structures. This research provided a new screening procedure for finding selective candidate compounds and appropriate docking models of a target by considering the structure diversity of PDB structures, which was applied to discovery novel selective FXR agonists to treat hyperlipidemia.

Communicated by Ramaswamy H. Sarma     

Capturing of the free cysteine residue in the ligand-binding site by affinity labeling of the ORL1 nociceptin receptor

All of the δ, μ, and κ opioid receptors have a free thiol group of the Cys residue in the ligand-binding site, although its functional role is not yet known. In order to examine whether or not a similar Cys is also present in the ORL1 nociceptin receptor, we attempted to identify it by affinity labeling using a specific antagonist peptide. We first treated ORL1-expressing COS-7 cell membrane preparations with the thiol-alkylation reagent N-ethylmaleimide (NEM) to perform a binding assay using [³H]nociceptin as a tracer and nociceptin, an ORL1 agonist, or Ac-Arg-Tyr-Tyr-Arg-Ile-Lys-NH₂, a nociceptin/ORL1 antagonist, as a competitor. It was suggested that ORL1 has a free Cys in its ligand-binding site, since the NEM treatment reduced the population of ligand-binding sites. This was further confirmed by affinity labeling using Cys(Npys)-Arg-Tyr-Tyr-Arg-Ile-Lys-NH₂ with the SNpys group that can react with a free thiol group, resulting in the formation of a disulfide bond. This affinity labeling was approximately 23 times more specific than NEM alkylation. The results revealed that the ORL1 nociceptin receptor does contain a free Cys residue in the ligand-binding site.     

Discovery of HWL-088: A highly potent FFA1/GPR40 agonist bearing a phenoxyacetic acid scaffold

Based on a previously reported phenoxyacetic acid scaffold, compound 7 (HWL-088) has been identified as a superior free fatty acid receptor 1 (FFA1) agonist by comprehensive structure-activity relationship study. Our results indicated that the introduction of ortho-fluoro greatly increased the activity of phenoxyacetic acid series, and the unique structure-activity relationship in biphenyl moiety is different from previously reported FFA1 agonists. Moreover, the modeling study was also performed to better understand the binding mode of present series. Compound 7 significantly improved glucose tolerance both in normal and diabetic models, and even exerted greater potential on glucose control than that of TAK-875. These findings provided a novel candidate HWL-088, which is currently in preclinical study to evaluate its potential for the treatment of diabetes.     

Exploring subtype selectivity and metabolic stability of a novel series of ligands for the benzodiazepine binding site of the GABAA receptor

A novel series of agonists at the benzodiazepine binding site of the GABA_A receptor was prepared by functionalizing a known template. Adding substituents to the pyrazolone-oxygen of CGS-9896 led to a number of compounds with selectivities for either α2- or α1-containing GABA_A receptor subtypes offering an entry into indications such as anxiety and insomnia. In this communication, structure-activity relationship and efforts to increase in vitro stabilities are discussed.     

Synthesis and SAR studies of 3-phenoxypropyl piperidine analogues as ORL1 (NOP) receptor agonists

A series of 3-phenoxypropyl piperidine analogues have been discovered as novel ORL1 receptor agonists. Structure-activity relationships have been explored around the 3-phenoxypropyl region with several potent and selective analogues identified.     

Effect of novel N-aryl sulfonamide substituted 3-morpholino arecoline derivatives as muscarinic receptor 1 agonists in Alzheimer's dementia models

A series of novel, potent, and selective muscarinic receptor 1 agonists (M1 receptor agonists) that employ a key N-substituted morpholine Arecoline moiety has been synthesized as part of research effort for the therapy of Alzheimer’s diseases. The ester group of arecoline (which is reported as muscarinic agonist) has been replaced by N-substituted morpholine ring. The structure–activity relationship reveals that the electron donating 4-substituted sulfonyl derivatives (9a, 9b, 9c, and 9e) on the nitrogen atom of the morpholine ring increases the affinity of M1 receptor binding 50- to 80-fold greater than the corresponding arecoline. Other derivatives also showed considerable M1 receptor binding affinity.