靶向神经小胶质细胞的戒毒治疗策略

鸦片用于镇痛治疗有千余年历史, 其滥用导致药物成瘾, 带来严重的社会和医学问题。关于鸦片等精神活性物质的研究主要围绕 神经元,当前的戒毒药物作用于神经元的阿片受体或离子通道受体,然而其戒毒效果非常有限。神经元不是中枢神经系统中调节神经信号 转导的唯一组分,神经小胶质细胞占中枢神经系统的 10%~15%,然而其作用和功能在很长一段时间被忽视。鸦片、可卡因、冰毒及其他 精神活性物质激活 Toll 样受体 4 (TLR4),活化小胶质细胞,产生大量炎症因子,从而调节奖赏信号通路,增加神经元的兴奋性,导致药物 依赖和成瘾,因而 TLR4 是开发新型戒毒药物的靶点。综述药物成瘾的小胶质细胞分子机制以及靶向小胶质细胞的治疗药物成瘾的药物发现。     

胶质细胞源性神经营养因子对疼痛的调节作用

胶质细胞源性神经营养因子(glial cell derived neurotrophic factor,GDNF)属转化生长因子β超家族成员,其成熟蛋白由134个氨基酸残基组成,而GDNF受体广泛分布于外周和中枢神经系统。GDNF不仅可以促进多巴胺能神经元、运动神经元的存活,对交感、副交感以及感觉神经元具有营养作用,还能够影响神经元的发育、分化并对非神经系统的发育也具有重要作用。近年来随着人们对疼痛认识的深入,疼痛的机制也不再限于神经元功能的改变,还受胶质细胞活化、多种营养因子、细胞因子及相应受体、离子通道等多方面因素的影响。为此,本文就近年来GDNF参与疼痛调节的相关研究进展做一简要综述。     

胶质源性神经营养因子对不同组织细胞的影响

GDNF来自于小胶质神经元,首先作为中脑多巴胺能神经元的复活因子被发现,可促进细胞存活,并有增加多巴胺神经元细胞大小及轴突长度的作用。GDNF通过与锚定蛋白细胞表面受体糖基磷脂酰肌醇的相互作用来调节细胞活性。GDNF家族a-1受体,通过跨膜酪氨酸受体或者神经元细胞黏附分子,来促进细胞存活,神经突生长,以及突触发育。后续的研究提示,无论未成年还是成体大脑,GDNF对多种神经细胞都有复活的作用,并与一些周围神经复活、迁移、分化相关。不同的脑缺血实验模型均证实了外源性GDNF对于病灶部位及全脑的神经保护作用,包括局部应用营养因子,利用病毒载体运载GDNF基因以及移植表达GDNF的细胞。近来研究还证实,GDNF不仅对多巴胺能神经元,中枢和周围神经系统的运动、感觉神经元,以及自主神经元有营养和保护作用,对于非神经系统也有不同调节作用。本文将重点讨论这些GDNF作用的不同策略以及机制。     

星形胶质细胞功能障碍在抑郁症发病中的作用研究进展

星型胶质细胞在突触形成、神经元代谢、神经递质传递等方面起重要作用,其退行性病变可引起突触蛋白水平降低、神经元体积减小及神经递质传递异常,进而引起神经精神性疾病的发生。抑郁症患者前额叶皮层、海马、杏仁核以及前扣带回等多个脑区均有星型胶质细胞密度减低,提示星形胶质细胞与抑郁症发病密切相关。研究表明,能量和营养支持、谷氨酸(glutamate,Glu)转运和代谢、N-甲基-D-天(门)冬氨酸(N-methyl-D-aspartate,NMDA)受体活性调节以及炎症反应异常等星形胶质细胞功能障碍参与抑郁症的发生。本文就星形胶质细胞功能障碍在抑郁症发病机理中的作用进行综述。     

谷氨酸、NMDA 和吗啡对培养大鼠星形胶质细胞内钙振荡的影响

目的:研究谷氨酸、NMDA、吗啡对原代培养的大鼠星形胶质细胞的胞内钙信号的影响及受体作用机制.方法:利用Leica AF6000活细胞工作站,检测谷氨酸、NMDA、吗啡分别灌流前后Fura-2/AM加载的星形胶质细胞内钙信号的动态变化,进一步观 察分别阻断代谢性谷氨酸受体5 (mGluR5)、NMDA受体(NMDA receptor,NMDAR)和阿片μ受体对诱导的胞内钙振荡的影响.结果:谷氨酸、NMDA、吗啡均可明显升高胞内游离钙的浓度([Ca2+]i),而将其相应受体拮抗后,星形胶质细胞[Ca2+]i升高的现象可以被显著抑制.结论:离体培养的星形胶质细胞膜上存在mGluR5、NMDAR和阿片μ受体,这些受体的激活可以升高星影胶质细胞的[Ca2+]i,且这些受体依赖的[Ca2+]i的调控机制可能是星形胶质细胞与神经元交互作用的重要途径之一.     

血管内皮生长因子促损伤脑内神经血管单元的重构

血管内皮生长因子(vascular endothelial growth factor,VEGF)最初被认为是调节血管内皮细胞通透性及血管增生的生物活性物质。后来发现,VEGF在脑内的神经细胞也有表达,并参与神经细胞的发育、轴突的生长和神经元细胞膜上离子通道功能的调节。VEGF对损伤脑具有抗凋亡等神经保护作用。此外,VEGF还具有促进损伤脑内神经元新生的作用和增强活化胶质细胞转分化为新生神经元的能力。现有的文献提示,VEGF在正常脑内能调节神经可塑性,在损伤的脑内能促进神经血管单元的重构和脑修复。本文重点阐述成年脑内VEGF对神经细胞的生物学效应及其对损伤脑的修复作用。深入研究VEGF的神经调节作用及其机制,有助于理解脑功能调节机制,研发脑保护和脑修复的新技术。     

死亡受体在神经系统疾病中的作用及在神经系统中的下游信号传送机制

细胞凋亡在神经系统发育、神经系统疾病和外伤中扮演着重要角色。死亡受体不仅能触发细胞凋亡,还能促进细胞的生存和生长。最近研究显示,部分死亡受体在神经发育或退化等方面发挥着重要作用。死亡受体在帕金森病中具有神经保护的作用,在肌萎缩性脊髓侧索硬化和脑缺血性疾病中诱发凋亡前体的产生。这种不同的功能反映出在神经元和神经胶质细胞中死亡受体在转录和翻译信号通路下游的不同机制。本文就死亡受体在神经系统发育和疾病中的作用及其细胞内信号通路作一综述。     

胶质细胞生长因子的研究进展

胶质细胞生长因子(glial growth factor,GGF)是neuregulin基因的产物。GGF与erbB受体的异二聚体或同二聚体结合,催化多肽链中的酪氨酸磷酸化,激活下游信号分子而发挥其生理作用。GGF及其受体在发育及成熟神经系统中广泛分布。GGF限定神经嵴细胞,使其向雪旺氏细胞分化,并在雷旺氏细胞发育过程中发挥重要作用。GGF能够刺激少突胶质细胞前体细胞、少突胶质细胞和星形胶质细胞增殖,抑制少突胶质细胞前体细胞分化成少突胶质细胞,抑制O-2A细胞分化成星形胶质细胞。GGF能够促进神经元沿着放射状的胶质细胞迁移,促进培养的视网膜神经元存活和突触生长。     

脑星形胶质细胞生物学功能研究进展

脑星形胶质细胞是中枢神经系统（CNS）内在数目占绝对优势的一类大胶质细胞,被认为在神经元的整个发育过程中起重要作用。本文主要就参与星形胶质细胞调节神经元活动的主要功能分子,星形胶质细胞在中枢神经系统的生物学功能,及其与疾病的关系作一简要回顾。     

小脑皮质结构年龄相关变化的研究进展

衰老过程中小脑皮质出现明显的形态学变化,包括体积萎缩、重量减轻、皮层厚度下降、神经元数量减少,树突丢失、细胞超微结构改变、神经递质紊乱以及胶质细胞增生等。神经元数量丢失与结构退变以及神经递质改变可能会导致老年小脑皮质神经环路破坏和信息传输紊乱,与老年个体运动调节功能及运动学习能力下降有关;神经胶质活动增强对维持老年小脑皮质的形态和功能可能起保护作用。     

Modulation of extracellular signal-regulated kinase (ERK) activity by acute and chronic opioid treatment in neuronal and glial cell lines

Acute mu opioid application has been shown to activate extracellular signal-related kinases (ERKs) in various non-neural cell lines. However, ERK activation in neuronal cells following acute morphine treatment is more questionable. Moreover, the ERK activation phenomenon observed in vivo after withdrawal of chronic opioids has never been demonstrated in vitro. The goal of this study was to determine if mu agonist treatment induced ERK activation acutely or after withdrawal of chronic opioids in one glial and three neuronal cell lines. We found that acute application of opioids was not able to activate ERK in neuronal cell lines but was able to activate ERK in a glial cell line. In another set of experiments, cells were chronically treated with escalating doses of a mu opioid agonist. After 8 days, the agonist was removed from the media and naloxone applied. Acute ERK activation was not seen in any tested cell line after agonist removal. These findings suggest that opioids may acutely activate ERK in non-neuronal cells, and that the acute ERK activation observed in some brain regions during opioid withdrawal in vivo might be mediated by indirect effects on neuronal cells.     

Endogenous opioids and feeding behavior: A decade of further progress (2004–2014). A Festschrift to Dr. Abba Kastin

Functional elucidation of the endogenous opioid system temporally paralleled the creation and growth of the journal, Peptides, under the leadership of its founding editor, Dr. Abba Kastin. He was prescient in publishing annual and uninterrupted reviews on Endogenous Opiates and Behavior that served as a microcosm for the journal under his stewardship. This author published a 2004 review, “Endogenous opioids and feeding behavior: a thirty-year historical perspective”, summarizing research in this field between 1974 and 2003. The present review “closes the circle” by reviewing the last 10 years (2004–2014) of research examining the role of endogenous opioids and feeding behavior. The review summarizes effects upon ingestive behavior following administration of opioid receptor agonists, in opioid receptor knockout animals, following administration of general opioid receptor antagonists, following administration of selective mu, delta, kappa and ORL-1 receptor antagonists, and evaluating opioid peptide and opioid receptor changes in different food intake models.     

Opioids modulate periodicity rather than efficacy of peristaltic waves in the guinea pig ileum in vitro

The influence of opioid receptor blockade by naloxone and opioid receptor activation by opioids on peristalsis was studied in isolated segments of the guinea pig ileum.1. (-)Naloxone, but not (+)naloxone, increased the mean number of peristaltic waves per min within periods of elevated intraluminal pressure. Naloxone tended to modify intermittent peristalsis into ongoing peristalsis, whereas opioids worked in an opposite fashion. 2. Maximum amplitudes of luminal volume displacement during single peristaltic waves were not decreased by opioids. (-)Naloxone, however, applied to non-pretreated segments, decreased transitorily the efficacy of single peristaltic waves to a small, but statistically significant degree 3. Enhancement of peristalsis by naloxone decreased over time, although enough naloxone was present to occupy all opioid receptors. This suggests that opioid receptor blockade induces some compensatory mechanism.     

Structural characteristics of two highly selective opioid peptides

The demonstration of opioid receptors by radioligand binding and the discovery of their endogenous peptide ligands has provided a new class of compounds that can be used for the development of novel opioids. The number of potential receptor targets for such opioids has been expanded by the identification of multiple opioid receptor types. The development of highly selective opioid peptides using the principles of conformational restriction permits the analysis of the structure-activity requirements of each receptor type, and is facilitating the elucidation of the functional properties of the different opioid receptors.     

Opioid and nociceptin receptors regulate cytokine and cytokine receptor expression

Opioids were originally discovered because of their ability to induce analgesia, but further investigation has shown that the opioids regulate the function of cells involved in the immune response. We suggest that the regulation of cytokine, chemokine, and cytokine receptor expression is a critical component of the immunomodulatory activity of the opioids. In this paper we review the literature dealing with the regulation of cytokine and cytokine receptor expression by agonists for the three major opioid receptor types (mu, kappa, and delta), and nociceptin, the natural agonist for the orphanin FQ/nociceptin receptor. Although the opioid receptors share a high degree of sequence homology, opposing roles between the kappa opioid receptor (KOR) and the mu opioid receptor (MOR) have become apparent. We suggest that activation of the KOR induces an anti-inflammatory response through the down-regulation of cytokine, chemokine and chemokine receptor expression, while activation of the MOR favors a pro-inflammatory response. Investigation into the opioid receptor-like (ORL1)/nociceptin system also suggests a role for this receptor as a down-regulator of immune function. These effects suggest a broad role for opioids in the modulation of the function of the immune system, and suggest possible targets for the development of new therapeutics for inflammatory and infectious diseases.     

Opioids in the regulation of food intake and energy expenditure

This paper and the following four papers summarize a symposium on the role of opioids in regulation of feeding, body weight, and energy expenditure. The central sites of opioid action are discussed, as is opioid activity in invertebrates, large animals, and humans. This paper provides a historical review of developments in the field from the early concepts of an endogenous opioid system to the current understanding of multiple receptor types and their interaction in regulating ingestive behavior. Opioids from all three opioid families may stimulate food intake, and some evidence exists that opioids may stimulate energy expenditure. Eating and drinking behavior is very complex and involves a number of components. Our understanding of the role of opioids in this process is shallow, and future research must be designed carefully to evaluate individual components of ingestive behavior.     

Morphine and Fentanyl Repeated Administration Induces Different Levels of NLRP3-Dependent Pyroptosis in the Dorsal Raphe Nucleus of Male Rats via Cell-Specific Activation of TLR4 and Opioid Receptors

Morphine promotes neuroinflammation after NOD-like receptor protein 3 (NLRP3) oligomerization in glial cells, but the capacity of other opioids to induce neuroinflammation and its relationship to the development of analgesic tolerance is unknown. We studied the effects of morphine and fentanyl on NLRP3 inflammasome activation in glial and neuronal cells in the dorsal raphe nucleus (DRN), a region involved in pain regulation. Male Wistar rats received i.p. injections of morphine (10 mg/kg) or fentanyl (0.1 mg/kg) 3?×?daily for 7 days and were tested for nociception. Two hours after the last (19th) administration, we analyzed NLRP3 oligomerization, caspase-1 activation and gasdermin D-N (GSDMD-N) expression in microglia (CD11b positive cells), astrocytes (GFAP-positive cells) and neurons (NeuN-positive cells). Tolerance developed to both opioids, but only fentanyl produced hyperalgesia. Morphine and fentanyl activated NLRP3 inflammasome in astrocytes and serotonergic (TPH-2-positive) neurons, but fentanyl effects were more pronounced. Both opioids increased GFAP and CD11b immunoreactivity, caspase-1 and GSDMD activation, indicating pyroptotic cell death. The opioid receptor antagonist (?)-naloxone, but not the TLR4 receptor antagonist (+)-naloxone, prevented microglia activation and NLRP3 oligomerization. Only (+)-naloxone prevented astrocytes’ activation. The anti-inflammatory agent minocycline and the NLRP3 inhibitor MCC950 delayed tolerance to morphine and fentanyl antinociception and prevented fentanyl-induced hyperalgesia. MCC950 also prevented opioid-induced NLRP3 oligomerization. In conclusion, morphine and fentanyl differentially induce cell-specific activation of NLRP3 inflammasome and pyroptosis in the DRN through TLR4 receptors in astrocytes and through opioid receptors in neurons, indicating that neuroinflammation is involved in opioid-induced analgesia and fentanyl-induced hyperalgesia after repeated administrations.

     

Morphine regulates gene expression of alpha- and beta-chemokines and their receptors on astroglial cells via the opioid mu receptor

The brain is a target organ for recreational drugs and HIV-1. Epidemiological data demonstrate that opioid abuse is a risk factor for HIV-1 infection and progression to AIDS. Chemokines and their receptors have been implicated in the neuropathogenesis of HIV-1 infections. However, little is known about the effects of opioids on the expression of chemokines and their receptors (the latter also are HIV-1 coreceptors) by cells of the CNS. Herein we describe the effects of morphine on gene expression of the alpha- and beta-chemokines and their receptors by the astrocytoma cell line U87 and by primary normal human astrocyte (NHA) cultures. U87 cells treated with morphine showed significant down-regulation of IL-8 gene expression, whereas expression of the IL-8 receptor CXCR2 was reciprocally up-regulated as detected by RT-PCR. Treatment of NHAs with morphine suppressed IL-8 and macrophage-inflammatory protein-1beta gene expression, whereas expression of their receptor genes, CCR3 and CCR5, was simultaneously enhanced. These morphine-induced effects on U87 and NHA cells were reversed by the opioid mu receptor antagonist beta-funaltrexamine. Morphine also enhanced the constitutive expression of the opioid mu receptor on astroglial cells. Our results support the hypothesis that opioids play a significant role in the susceptibility of the CNS to HIV-1 infection and subsequent encephalopathy by inhibiting local production of HIV-1-protective chemokines (IL-8 and macrophage-inflammatory protein-1beta) and enhancing expression of HIV-1 entry coreceptor genes (CCR3, CCR5, and CXCR2) within the CNS. These effects of opioids appear to be mediated through the opioid mu receptor that we demonstrated on astroglial cells.     

Effect of prolonged progesterone treatment on the proenkephalin mRNA gene expression and enkephalins concentration in the sheep brain

The opioids modulate reproduction in sheep mostly by inhibiting the activity of the hypothalamo-pituitary-gonadal axis. However, the mechanism by which the negative feedback control systems regulate opioid synthesis and secretion in sheep is still not recognized. As a part of a research dealing with interaction between opioids and steroids, the effect of prolonged administration of progesterone (P4) and opioid receptor agonist or antagonist on the Met-enkephalin synthesis and concentration was examined in sheep brain. Long term P4 treatment significantly decreased the synthesis and the concentration of the opioid peptide in the hypothalamus and pituitary, however, the effect was more pronounced in the hypothalamus. Injections of Met-enkephalin completely or partially reversed the effect of P4. Naltrexone given together with opioid peptide modulated the response to the opioid agonist. The results show that there is an interaction between P4 and endogenous opioids in the central nervous system of cyclic sheep.     

Pharmacological Characterization of an Opioid Receptor in the Ciliate Tetrahymena

A pharmacological characterization has been performed of the opioid receptor involved in modulation of phagocytosis in the protozoan ciliate Tetrahymena. Studies on inhibition of phagocytosis by mammalian prototypic opioid agonists revealed that morphine and β-endorphin have the highest intrinsic activity, whereas all the other opioids tested can only be considered partial agonists. However, morphine (a mu-receptor agonist) is twice as potent as β-endorphin (a delta-receptor agonist). Furthermore, the sensitivity for the opioid antagonist naloxone, determined in the presence of morphine and β-endorphin, is very similar to the sensitivity exhibited by mammalian tissues rich in mu-opioid receptors. We suggest that the opioid receptor coupled to phagocytosis in Tetrahymena is mulike in some of its pharmacological characteristics and may serve as a model system for studies on opioid receptor function and evolution.