GABA受体激动剂对氧-葡萄糖剥夺诱导皮层神经元死亡的保护作用

目的:研究GABA受体激动剂对氧-葡萄糖剥夺诱导皮层神经元死亡的保护作用。方法:培养12d的皮层神经元更换为Earle's平衡盐溶液(Earle's balanced salts,EBSS)后置于37℃三气缺氧(N2:CO2:O2=94%:5%:1%)培养箱内培养,4h后恢复正常条件培养,同时在培养液内加入GABA A受体和B受体激动剂作用24h,用Hoechst33342/PI的染色方法检测其死亡情况。结果:GABA A受体激动剂(musci mol)和GABA B受体激动剂(baclofen)均分别能显著降低神经细胞死亡率49.9%和35.3%。结论:GA-BA A受体激动剂和B受体激动剂对氧-葡萄糖剥夺诱导的皮层神经元死亡均有显著的保护作用。     

从组胺H3受体的配体开发新药的展望

近年通过克隆技术鉴定了组胺H3和H4亚型受体。H3受体是突触前受体，其功能为调节组胺的生物合成与从末梢释放。在其他神经元也有H5受体的存在，因而还能调节其他若干神经递质的释放。已经发现了一些H3受体的激动剂与拮抗剂，实验研究表明这些激动剂与拮抗剂有广泛的生物作用。迄今尚未有这类化合物经批准在临床应用，但从其功用来日可能开发出一些有效药物。     

G蛋白偶联受体组成性活性及反向激动剂研究进展

G蛋白偶联受体（GPCR）是受体中家族成员最多的一大类，其活性涉及体内绝大部分的生理功能，在药物研发过程中是主要的药物作用靶标。研究表明，GPCR及其突变体在缺乏配体结合的情况下，能自发地产生一定程度的内在活性，即GPCR的组成性活性（constitutive activity）；其相应的反向激动剂与GPCR结合能降低受体的组成性活性，在药物治疗学上具有重要意义。愈来愈多的实验表明，GPCR组成性活性及反向激动剂的研究具有广阔和实际的应用前景，对其进行深入研究在受体学说领域和药物研发过程中具有重要理论意义。     

β_2-肾上腺素受体激动剂对哮喘气道炎症的拮抗作用

综述β2-肾上腺素受体激动剂对炎症细胞、细胞因子、炎症介质、趋化因子和黏附分子的作用及对血管通透 性的影响,探讨其抗炎作用机制。β2-受体激动剂长期以来一直作为支气管扩张药应用于哮喘治疗,近年来的实验及 临床研究证明β2-受体激动剂对哮喘气道炎症具有一定的抑制作用。     

新止痒镇痛阿片κ激动剂

nalfurafinehydrochloride(TRK 82 0 )在体外用电刺激的豚鼠回肠纵肌和小鼠输精管测定了nalfurafinehydrochloride(TRK 82 0 )的受体选择性和激动剂活性 (纳洛酮用于 μ受体 ,纳屈吲哚用于δ受体 ,norbinaltorphimine用于κ受体测试 )。TRK 82 0对以上两种组织的效应均比吗啡强 4 0 0 0倍 ,(豚鼠回肠IC50 =0 .0 0 4 8nmol·L- 1,小鼠输精管IC50 =0 .0 36nmol·L- 1) ,对κ受体有高选择性 (豚鼠回肠 μ/κ =2 79,小鼠输精管δ/κ =135 )。在表达大鼠野生型 μ ,δ和κ阿片受体的CHO细胞膜标本上进一步测定了TRK - 82 0的激动剂活性…     

阿片受体激动剂研究进展

疼痛是机体在受到伤害时的一种反馈而产生令人不快的主观感受,起到警示机体存在实质性或潜在的组织损伤的作用。治疗和缓解疼痛的主要药物是阿片受体激动剂,而传统的阿片受体激动剂存在阿片样副作用（包括成瘾性、耐受性、呼吸抑制性等）,从而限制其广泛应用。科研工作者寻找出许多规避副作用的策略,着重介绍在μ-阿片受体激动剂的设计和应用中消除阿片样副作用的传统策略和新型策略,简要介绍κ-阿片受体激动剂的最新研究进展,以期为镇痛药的研发及临床治疗提供新的思路。

     

治疗糖尿病和肥胖症的胃肠道激素类多受体激动剂研究进展

胰高血糖素样肽-1(glucagon-like peptide-1,GLP-1)类似物已广泛用于糖尿病和肥胖症的治疗，而将GLP-1类似物与其他肠道激素如葡萄糖依赖的促胰岛素肽、胰高血糖素结合的多受体激动剂正处于临床开发阶段。与GLP-1类似物相比，多受体激动剂可发挥多重生理效应、控制血糖和降低体重的效果更好、不良反应更小，有望成为糖尿病和肥胖症的新疗法。本文对在研的肠道激素类多受体激动剂进行综述，总结其设计思路及临床表现，为多受体激动剂类药物的开发提供参考。     

β2-肾上腺素受体激动剂对哮喘气道炎症的拮抗作用

综述β2-肾上腺素受体激动剂对炎症细胞、细胞因子、炎症介质、趋化因子和黏附分子的作用及对血管通透性的影响，探讨其抗炎作用机制。β2-受体激动剂长期以来一直作为支气管扩张药应用于哮喘治疗，近年来的实验及临床研究证明β2-受体激动剂对哮喘气道炎症具有一定的抑制作用。     

受点外位点：最新动态及其与长效β2受体激动剂作用时间的关系

四种β２肾上腺素受体激动剂克仑特罗，班布特罗，福莫特罗和沙美特罗均为长效支气管扩张剂，它们各有不同的作用机制。有证据表明，在β２肾上腺素受体除存在与配体结合的效应性或活性受点之外，咖有与沙美特罗有关化合物特异性结合的位点即受点外位点的存在。     

用分子模构法建立κ阿片受体激动剂的药效基团

目的：建立非肽类κ阿片受体激动剂的药效基团。方法：从ＭＤＬ ＭＤＤＲ数据库中选出五个高活性非肽类κ阿片受体激动剂，以四氢吡咯环Ｎ原子和乙酰胺基团为叠加点，用分子模构法建立非肽类κ阿片受体激动剂的药效基团。结果：四氢吡咯环、乙酰胺的羰基和与惭酰胺相连的疏水基团为非肽类κ阿片受体激动剂共同结构特征。推测受体Ａｓｐ１３８与甲氢吡咯环的Ｎ原子构成氢键，Ｓｅｒ１８７可能与激动剂的乙酰胺羰基以氢键形式相作用。     

Agonist binding, agonist affinity and agonist efficacy at G protein-coupled receptors

Measurements of affinity and efficacy are fundamental for work on agonists both in drug discovery and in basic studies on receptors. In this review I wish to consider methods for measuring affinity and efficacy at G protein coupled receptors (GPCRs). Agonist affinity may be estimated in terms of the dissociation constant for agonist binding to a receptor using ligand binding or functional assays. It has, however, been suggested that measurements of affinity are always contaminated by efficacy so that it is impossible to separate the two parameters. Here I show that for many GPCRs, if receptor/G protein coupling is suppressed, experimental measurements of agonist affinity using ligand binding (K(obs)) provide quite accurate measures of the agonist microscopic dissociation constant (KA). Also in pharmacological functional studies, good estimates of agonist dissociation constants are possible. Efficacy can be quantitated in several ways based on functional data (maximal effect of the agonist (E(max)), ratio of agonist dissociation constant to concentration of agonist giving half maximal effect in functional assay (K(obs)/EC50), a combined parameter E(max)K(obs)/EC50). Here I show that E(max)K(obs)/EC50 provides the best assessment of efficacy for a range of agonists across the full range of efficacy for full to partial agonists. Considerable evidence now suggests that ligand efficacy may be dependent on the pathway used to assess it. The efficacy of a ligand may, therefore, be multidimensional. It is still, however, necessary to have accurate measures of efficacy in different pathways.     

Minor Structural Change to Tertiary Sulfonamide RORc Ligands Led to Opposite Mechanisms of Action

相似文献   

Some implications of receptor theory for in vivo assessment of agonists, antagonists and inverse agonists

Drug effects can be classified into three major phenotypes: agonist, antagonist and inverse agonist. Agonist and inverse agonist effects are associated with receptor activation and inactivation, respectively, whereas antagonism implies that a drug produces no effect when administered alone but blocks the effects of agonists and inverse agonists. Attention has only recently begun to focus on the theoretical and clinical implications of inverse agonists, and studies of inverse agonism have also stimulated revisions in receptor theory. This commentary addresses two specific issues related to the application of receptor theory to studies of inverse agonists in vivo. First, principles of receptor theory suggest that increasing drug doses produce a graded pharmacological stimulus that is transduced by receptor-containing tissue into a biological response. However, assays vary in their ability to detect those responses, and any given assay provides only a narrow window on the full range of underlying drug effects. Consequently, in vivo assessment of inverse agonists will benefit from development of assays sensitive to graded inverse agonist effects. Second, detection of inverse agonist effects requires some preexisting level of receptor activity (or tone). This tone can result from at least two sources: (a) endogenous ligands for the receptor, or (b) constitutive receptor activity. Strategies for discriminating these two sources of tone will also contribute to the in vivo assessment of inverse agonist effects. Studies with intermediate efficacy ligands may be especially helpful in this regard, because their effects are differentially influenced by endogenous agonist tone versus constitutive receptor tone.     

Differential agonist and inverse agonist profile of antipsychotics at D2L receptors coupled to GIRK potassium channels

The D(2) dopaminergic receptor represents a major target of antipsychotic drugs. Using the coupling of the human D(2long) (hD(2L)) receptor to G protein-coupled inward rectifier potassium (GIRK) channels in Xenopus laevis oocytes, we examined the activity of antipsychotic agents of different classes - typical, atypical, and a "new generation" of compounds, exhibiting a preferential D(2) and 5-HT(1A) receptor profile. When the hD(2L) receptor was coexpressed with GIRK channels, a series of reference compounds exhibited full agonist (dopamine, and quinpirole), partial agonist (apomorphine, (-)3-PPP, and (+)-UH232) or inverse agonist (raclopride, and L741626) properties. Sarizotan exhibited only very weak partial agonist action. At higher levels of receptor cRNA injected per oocyte, both partial agonist activity and inverse agonist properties were generally more pronounced. The inverse agonist action of L741626 was reversed by interaction with sarizotan, thus confirming the constitutive activity of wild-type hD(2L) receptors in the oocyte expression system. When antipsychotic agents were tested for their actions at the hD(2L) receptor, typical (haloperidol) as well as atypical (nemonapride, ziprasidone, and clozapine) compounds acted as inverse agonists. In contrast, among D(2)/5-HT(1A) antipsychotics, only SLV313 and F15063 behaved as inverse agonists, whilst the other members of this group (bifeprunox, SSR181507 and the recently marketed antipsychotic, aripiprazole) exhibited partial agonist properties. Thus, the X. laevis oocyte expression system highlights markedly different activity of antipsychotics at the hD(2L) receptor. These differential properties may translate to distinct therapeutic potential of these compounds.     

Typical antipsychotics exhibit inverse agonist activity at rat dopamine D1-like receptors expressed in Sf9 cells

The baculovirus system has been used to express the rat dopamine D1 receptors in Spodoptera frugiperda (Sf9) cells. A panel of typical antipsychotics including, -flupenthixol, fluphenazine and thioridizine were found to inhibit dopamine-dependent stimulation of adenylyl cyclase. However, these compounds were also found to inhibit adenylyl cyclase activity in the absence of agonist in Sf9 cells expressing dopamine D1-like receptors. Therefore, these nonselective dopamine receptor compounds displayed negative intrinsic or inverse agonist activity. None of the compounds tested were neutral antagonists.     

Differences between human wild-type and C23S variant 5-HT2C receptors in inverse agonist-induced resensitization

The aim of this study was to analyze functional properties of the naturally occurring C23S variant of the human 5-HT2C receptor. In HEK293 cells transiently expressing the unedited forms of the variant receptor (VR) or the wild-type receptor (WTR), surface expression was determined by [3H]mesulergine binding to membrane fragments. Function was examined by an aequorin luminescence-based Ca2+ assay. Surface expression of the VR was 116% of that of the WTR. The 5-HT-induced increase in cytosolic Ca2+ ([Ca2+]i), and its inhibition by the inverse agonist SB 206553 did not differ between VR- or WTR-expressing cells. Preexposure of VR- or WTR-expressing cells to 0.5 μM 5-HT (3 min-4.5 h) led to a practically identical time course and extent in the reduction of the 5-HT-induced increase in [Ca2+]i. In contrast, prolonged preexposure to the inverse agonist SB 206553 (1 μM) elevated the 5-HT-induced increase in [Ca2+]i for both isoreceptors. A preexposure time of 4.5 h was necessary to significantly elevate the Ca2+ response of the WTR, but the VR produced this elevation within 1 h with virtually no further effect after 4.5 h of preexposure. In conclusion, prolonged preexposure to 5-HT caused equally rapid and strong desensitization of both isoreceptors. The different time course of SB 206553-induced resensitization of the two isoreceptors might be therapeutically relevant for drugs exhibiting inverse agonist properties at 5-HT2C receptors, such as atypical antipsychotics and certain antidepressants.     

Negative cooperativity in binding of muscarinic receptor agonists and GDP as a measure of agonist efficacy

BACKGROUND AND PURPOSE

Conventional determination of agonist efficacy at G-protein coupled receptors is measured by stimulation of guanosine-5′-γ−thiotriphosphate (GTPγS) binding. We analysed the role of guanosine diphosphate (GDP) in the process of activation of the M₂ muscarinic acetylcholine receptor and provide evidence that negative cooperativity between agonist and GDP binding is an alternative measure of agonist efficacy.

EXPERIMENTAL APPROACH

Filtration and scintillation proximity assays measured equilibrium binding as well as binding kinetics of [³⁵S]GTPγS and [³H]GDP to a mixture of G-proteins as well as individual classes of G-proteins upon binding of structurally different agonists to the M₂ muscarinic acetylcholine receptor.

KEY RESULTS

Agonists displayed biphasic competition curves with the antagonist [³H]-N-methylscopolamine. GTPγS (1 µM) changed the competition curves to monophasic with low affinity and 50 µM GDP produced a similar effect. Depletion of membrane-bound GDP increased the proportion of agonist high-affinity sites. Carbachol accelerated the dissociation of [³H]GDP from membranes. The inverse agonist N-methylscopolamine slowed GDP dissociation and GTPγS binding without changing affinity for GDP. Carbachol affected both GDP association with and dissociation from G_i/o G-proteins but only its dissociation from G_s/olf G-proteins.

CONCLUSIONS AND IMPLICATIONS

These findings suggest the existence of a low-affinity agonist-receptor conformation complexed with GDP-liganded G-protein. Also the negative cooperativity between GDP and agonist binding at the receptor/G-protein complex determines agonist efficacy. GDP binding reveals differences in action of agonists versus inverse agonists as well as differences in activation of G_i/o versus G_s/olf G-proteins that are not identified by conventional GTPγS binding.     

Differential inverse agonist efficacies of SB-258719, SB-258741 and SB-269970 at human recombinant serotonin 5-HT7 receptors

Recombinant 5-hydroxytryptamine 5-HT7 receptors are known to express constitutive, i.e., agonist-independent activity. Nonselective ligands, like methiothepin, ritanserin or clozapine behave as full inverse agonists at 5-HT7 receptors. The aim of the present study was to evaluate the degree of inverse agonist activity of three selective 5-HT7 receptor antagonists ((R)-3,N-dimethyl-N-[1-methyl-3-(4-methyl-piperidin-1-yl)propyl]benzene sulfonamide or SB-258719, R-(+)-1-(toluene-3-sulfonyl)-2-[2-(4-methylpiperidin-1-yl)ethyl]-pyrrolidine or SB-258741 and (R)-3-(2-(2-(4-methylpiperidin-1-yl)ethyl)-pyrrolidine-1-sulfonyl)-phenol or SB-269970) in the same model. cAMP accumulation was measured in intact Chinese hamster ovary (CHO) cells expressing human recombinant 5-HT7a receptors. In these cells, 5-HT stimulated cAMP levels and a series of ligands antagonized the effect of 5-HT with a 5-HT7 receptor-like profile. SB-258719 had no inverse agonist activity, SB-258741 behaved as a partial inverse agonist and SB-269970 was a quasi-full inverse agonist (as compared to methiothepin). The inverse agonist effect of SB-269970 was antagonized in a concentration-dependent manner by SB-258719. The widespread spectrum of inverse agonist activities shown by these compounds should help assessing the physiological relevance of constitutive 5-HT7 receptor activity in native tissues.     

Inverse agonism and its therapeutic significance

A large number of G-protein-coupled receptors (GPCRs) show varying degrees of basal or constitutive activity. This constitutive activity is usually minimal in natural receptors but is markedly observed in wild type and mutated (naturally or induced) receptors. According to conventional two-state drug receptor interaction model, binding of a ligand may initiate activity (agonist with varying degrees of positive intrinsic activity) or prevent the effect of an agonist (antagonist with zero intrinsic activity). Inverse agonists bind with the constitutively active receptors, stabilize them, and thus reduce the activity (negative intrinsic activity). Receptors of many classes (α-and β-adrenergic, histaminergic, GABAergic, serotoninergic, opiate, and angiotensin receptors) have shown basal activity in suitable in vitro models. Several drugs that have been conventionally classified as antagonists (β-blockers, antihistaminics) have shown inverse agonist effects on corresponding constitutively active receptors. Nearly all H(1) and H(2) antihistaminics (antagonists) have been shown to be inverse agonists. Among the β-blockers, carvedilol and bucindolol demonstrate low level of inverse agonism as compared to propranolol and nadolol. Several antipsychotic drugs (D(2) receptors antagonist), antihypertensive (AT(1) receptor antagonists), antiserotoninergic drugs and opioid antagonists have significant inverse agonistic activity that contributes partly or wholly to their therapeutic value. Inverse agonism may also help explain the underlying mechanism of beneficial effects of carvedilol in congestive failure, naloxone-induced withdrawal syndrome in opioid dependence, clozapine in psychosis, and candesartan in cardiac hypertrophy. Understanding inverse agonisms has paved a way for newer drug development. It is now possible to develop agents, which have only desired therapeutic value and are devoid of unwanted adverse effect. Pimavanserin (ACP-103), a highly selective 5-HT(2A) inverse agonist, attenuates psychosis in patients with Parkinson's disease with psychosis and is devoid of extrapyramidal side effects. This dissociation is also evident from the development of anxioselective benzodiazepines devoid of habit-forming potential. Hemopressin is a peptide ligand that acts as an antagonist as well as inverse agonist. This agent acts as an antinociceptive agent in different in vivo models of pain. Treatment of obesity by drugs having inverse agonist activity at CB(1/2) receptors is also underway. An exciting development is evaluation of β-blockers in chronic bronchial asthma-a condition akin to congestive heart failure where β-blockade has become the standard mode of therapy. Synthesis and evaluation of selective agents is underway. Therefore, inverse agonism is an important aspect of drug-receptor interaction and has immense untapped therapeutic potential.