基于神经胶质细胞的癌性疼痛机制及相关药物研究进展

导致癌痛的机制十分复杂,中枢神经系统的小胶质细胞和星形胶质细胞在癌痛的发生发展中起着重要的作用.活化的胶质细胞通过上调胶质标记物,激活细胞内的信号通路,上调胶质细胞受体和化学通道,下调转运蛋白,释放炎性介质参与癌痛的调节.作用于胶质细胞减轻癌痛的药物包括丙戊茶碱、 二甲胺四环素、D-型氨基酸氧化酶抑制剂、 脂氧素和中药提取物等.本文对胶质细胞参与癌痛调节机制及相关药物的研究进展作一综述.     

脊髓胶质细胞及前炎性细胞因子在慢性前列腺炎/慢性盆腔疼痛综合征大鼠中的作用及机制

目的探讨脊髓星形胶质细胞和小胶质细胞以及前炎性细胞因子白细胞介素-1β(IL-1β)、白细胞介素-6(IL-6)和肿瘤坏死因子α(TNFα)在CP/CPPS发生发展中的作用及机制。方法 40只健康雄性Sprague-Dawley(SD)大鼠,随机分为正常不加任何处理的对照组(n=20)、CP/CPPS模型组(n=20),完全福氏佐剂和3%角叉菜胶前列腺内注射造成CP/CPPS模型。通过检测机械性痛阈(PWT)来评价动物痛行为学改变;采用免疫组织化学、逆转录多聚酶链反应(RT-PCR)等方法,检测脊髓星形胶质细胞GFAP和小胶质细胞OX-42的表达以及脊髓前炎性细胞因子IL-1β、IL-6及TNFαmRNA表达的变化,评价脊髓小胶质细胞和星形胶质细胞活化情况及脊髓前炎性细胞因子表达与疼痛行为改变的关系。结果与对照组比较,CP/CPPS模型组大鼠建模后第11天出现PWT明显降低(P<0.05),并呈进行性下降趋势;随着时间进程,免疫组化结果显示模型组动物脊髓小胶质细胞和星形胶质细胞依次活化,小胶质细胞活化开始于建模后第7天,星形胶质细胞活化开始于建模后第14天;模型组动物脊髓IL-1β、IL-6和TNFαmRNA表达较对照组明显增加(P<0.05)。结论在CP/CPPS大鼠中脊髓胶质细胞活化及前炎性细胞因子IL-1β、IL-6和TNFα的表达增加,可能在神经病理性疼痛的产生和维持中起着重要的作用。     

神经胶质细胞在多发性硬化中的作用

多发性硬化是以炎性脱髓鞘病变为主要特征的中枢神经系统自身免疫性疾病。神经胶质细胞是中枢神经系统中除神经元外的另一大类细胞,目前研究证明神经胶质细胞在多发性硬化的炎性脱髓鞘过程中发挥了重要作用。本文对小胶质细胞、少突胶质细胞、星形胶质细胞在多发性硬化中的作用进行综述。     

调控环磷腺苷信号通路治疗病理性疼痛

病理性疼痛是困扰人类健康的一种常见疾患,寻找合适的治疗靶点控制病理性疼痛是目前疼痛研究的一个重要方向。近年的研究发现,活化的炎细胞、神经胶质细胞在病理性疼痛中发挥重要作用。环磷腺苷是存在于多种细胞内的第二信使,有文献报道促进环磷腺苷通路能抑制炎细胞及胶质细胞活性,进而治疗病理性疼痛。该文对环磷腺苷通路抑制炎细胞及胶质细胞活化的机制,以及磷酸二酯酶抑制剂治疗病理性疼痛的研究现状做一综述。     

A型肉毒毒素作用于神经胶质细胞缓解神经病理性疼痛机制的研究进展

神经病理性疼痛是一个重要的临床问题,常规药物治疗效果不佳。A型肉毒毒素可缓解多种疼痛,其镇痛作用被认为与神经胶质细胞相关。本文概要介绍A型肉毒毒素作用于神经胶质细胞缓解神经病理性疼痛机制的研究进展,进一步探究A型肉毒毒素在神经病理性疼痛治疗上的临床潜力。     

神经病理性疼痛发生机制的研究进展

为了获得高效治疗神经病理性疼痛的方法,本研究对近几年国内外神经病理性疼痛机制与治疗方面的研究进行分析。大量动物模型实验研究证实,脊髓背角星形胶质细胞激活、C-纤维的敏化调节、嘌呤受体信号的激活以及TNF-α细胞因子释放等途径或机制共同作用导致神经病理性疼痛的发生。针对这些机制的研究可指导临床从不同途径阻断疼痛的发生及发展过程,从而治疗该类疼痛,并可为通过减少外周刺激、提高疼痛阈值、阻断疼痛感觉传导等相应手段治疗神经病理性疼痛提供重要理论依据。     

脑细胞衰老在阿尔茨海默症发病机制中的潜在作用

细胞衰老的显著特征是永久的细胞周期停滞,同时伴随细胞代谢、表观遗传调控等变化。阿尔茨海默症(AD)是一种常见的神经退行性疾病,主要症状为记忆力减退和认知功能障碍。大量研究表明,星形胶质细胞和小胶质细胞等中枢神经系统细胞的衰老与AD的发生密切相关,抑制脑细胞衰老有望为AD的防治提供新思路和治疗策略。本文综述了脑细胞衰老在AD发病中的潜在作用及机制、脑细胞之间的相互影响,从而为AD病理机制研究及抗AD药物研发提供新的方向。     

P2X4受体结构及其参与神经病理性痛机制的研究进展

神经病理性痛是神经系统炎症或损伤后引发的一种慢性疼痛,其发病机制复杂,目前仍缺乏有效的治疗药物。近年来针对P2X4受体的蛋白结构及配体结合相关的重要部位开展了大量研究,发现表达于脊髓背角小胶质细胞的P2X4受体在神经病理性痛的发生和发展过程中具有重要的作用,提示其可能参与了神经病理性痛的发病。本文就P2X4受体的结构及其参与神经病理性痛的可能机制作一综述,试图为靶向P2X4受体研发新型抗神经病理性痛药物提供新的线索。     

小胶质细胞p38MAPK在病理性疼痛中作用的研究进展

有丝分裂原激活蛋白激酶(mitogen-activated protein kinase;MAPK)是不同的一类信号级联,目前认为脊髓小胶质细胞p38MAPK在病理性疼痛中有重要作用.本文综述了其在病理性疼痛中的研究进展.     

米诺环素对神经病理性疼痛大鼠脊髓星形胶质细胞激活的影响

目的观察米诺环素对CCI大鼠脊髓水平GFAP表达,探讨脊髓星形胶质细胞在神经病理性疼痛中的不同时程作用。方法将110只SD大鼠随机分成5组:A组:对照组(n=15)、B组:假手术组(n=25)、C组:CCI对照组(n=25)、D组:CCI预给药组(n=25)、E组:CCI治疗组(n=25)。分别测定各组在手术前(以第0天表示)以及手术后第1、4、7、11、14天损伤侧后肢50%机械刺激缩足阈值,然后相应分别取每组大鼠L4-6段脊髓,采用免疫组化染色方法测定脊髓背角星形胶质细胞GFAP表达变化情况。结果①坐骨神经结扎后大鼠出现痛觉过敏且持续增强存在。②B组和D组亦可见星形胶质细胞有轻微的激活,C组脊髓背角星形胶质细胞在术后7d发生明显激活,至术后14d星形胶质细胞被强烈的激活;E组星形胶质细胞术后有较明显的激活但无高峰期。结论脊髓水平星形胶质细胞的激活可能对神经病理性疼痛的产生维持发挥重要作用;米诺环素术前给药抑制星形胶质细胞的激活,减轻神经病理性疼痛。     

Spinal astrocytes as therapeutic targets for pathological pain

Development of next-generation analgesics requires a better understanding of the molecular and cellular mechanisms underlying pathological pain. Accumulating evidence suggests that the activation of glia contributes to the central sensitization of pain signaling in the spinal cord. The role of microglia in pathological pain has been well documented, while that of astrocytes still remains unclear. After peripheral nerve inflammation or injury, spinal microglia are initially activated and subsequently sustained activation of astrocytes is precipitated, which are implicated in the induction and maintenance of pathological pain. Astrocytic activation is caused by the production of diffusible factors from primary afferent neurons (neuron-to-astrocyte signals) and activated microglia (microglia-to-astrocyte signals). Although astrocyte-to-neuron signals implicated in pathological pain is poorly understood, activated astrocytes, as well as microglia, produce proinflammatory cytokines and chemokines, which lead to adaptation of the dorsal horn neurons. Furthermore, it has been suggested that glial glutamate transporters in the spinal astrocytes are down-regulated in pathological pain and that up-regulation or functional enhancement of these transporters prevents pathological pain. This review will briefly discuss novel findings on the role of spinal astrocytes in pathological pain and their potential as a therapeutic target for novel analgesics.     

Attenuation of morphine tolerance, withdrawal-induced hyperalgesia, and associated spinal inflammatory immune responses by propentofylline in rats.

The activation of glial cells and enhanced proinflammatory cytokine expression at the spinal cord has been implicated in the development of morphine tolerance, and morphine withdrawal-induced hyperalgesia. The present study investigated the effect of propentofylline, a glial modulator, on the expression of analgesic tolerance and withdrawal-induced hyperalgesia in chronic morphine-treated rats. Chronic morphine administration through repeated subcutaneous injection induced glial activation and enhanced proinflammatory cytokine levels at the lumbar spinal cord. Moreover, glial activation and enhanced proinflammatory cytokine levels exhibited a temporal correlation with the expression of morphine tolerance and hyperalgesia. Consistently, propentofylline attenuated the development of hyperalgesia and the expression of spinal analgesic tolerance to morphine. The administration of propentofylline during the induction of morphine tolerance also attenuated glial activation and proinflammatory cytokines at the L5 lumbar spinal cord. These results further support the hypothesis that spinal glia and proinflammatory cytokines contribute to the mechanisms of morphine tolerance and associated abnormal pain sensitivity.     

Modulation of microglia can attenuate neuropathic pain symptoms and enhance morphine effectiveness

Microglia play a crucial role in the maintenance of neuronal homeostasis in the central nervous system, and microglia production of immune factors is believed to play an important role in nociceptive transmission. There is increasing evidence that uncontrolled activation of microglial cells under neuropathic pain conditions induces the release of proinflammatory cytokines (interleukin - IL-1beta, IL-6, tumor necrosis factor - TNF-alpha), complement components (C1q, C3, C4, C5, C5a) and other substances that facilitate pain transmission. Additionally, microglia activation can lead to altered activity of opioid systems and neuropathic pain is characterized by resistance to morphine. Pharmacological attenuation of glial activation represents a novel approach for controlling neuropathic pain. It has been found that propentofylline, pentoxifylline, fluorocitrate and minocycline decrease microglial activation and inhibit proinflammatory cytokines, thereby suppressing the development of neuropathic pain. The results of many studies support the idea that modulation of glial and neuroimmune activation may be a potential therapeutic mechanism for enhancement of morphine analgesia. Researchers and pharmacological companies have embarked on a new approach to the control of microglial activity, which is to search for substances that activate anti-inflammatory cytokines like IL-10. IL-10 is very interesting since it reduces allodynia and hyperalgesia by suppressing the production and activity of TNF-alpha, IL-1beta and IL-6. Some glial inhibitors, which are safe and clinically well tolerated, are potential useful agents for treatment of neuropathic pain and for the prevention of tolerance to morphine analgesia. Targeting glial activation is a clinically promising method for treatment of neuropathic pain.     

The Role of Cytokines in the Initiation and Maintenance of Chronic Pain

Recent advancements in the pain field have identified a central nervous system (CNS) neuroimmune response that may act as the driving force for neuronal hypersensitivity, the pathological correlate to chronic pain following peripheral nerve injury. Neuroimmune activation involves the activation of nonneuronal cells such as endothelial and glial cells, which when stimulated leads to enhanced production of a host of inflammatory mediators, such as cytokines. The central production of proinflammatory cytokines, such as interleukin-1beta (IL-1beta), IL-6 and tumor necrosis factor have been found to play a key role in the propagation of persistent pain states. In addition, chemotactic cytokines, chemokines, have also been recently identified in the CNS neuroimmune cascade that ensues after injury to a peripheral nerve. The extravasation of leukocytes from the blood to the site of perceived injury is defined as the neuroinflammatory aspect of this cascade. Chemokines directly control this leukocyte transmigration process. They are synthesized at the site of injury and establish a concentration gradient through which immune cells migrate. Recent studies have demonstrated leukocyte trafficking into the CNS following peripheral nerve or lumbar nerve root injury. With the use of selective cytokine inhibitors and neutralizing antibodies, tactile and thermal hypersensitivity is attenuated in animal models of neuropathy. A further understanding of the role of nonneuronal cells, the physiological mechanisms of CNS cytokines and chemokines, and their relevance to neuro- immune activation and neuroinflammatory processes may lead to the development of novel pharmacological agents for the treatment and prevention of chronic pain. (c) 2002 Prous Science. All rights reserved.     

Chronic inflammatory pain and the neurovascular unit: a central role for glia in maintaining BBB integrity?

Pain is a complex phenomenon involving both a peripheral innate immune response and a CNS response as well as activation of the hypothalamic-pituitary-adrenal axis. The peripheral innate immune response to injury involves the rapid production and local release of proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-/alpha), interleukin-1 (IL-1) and IL-6. Recent studies into the CNS response to peripheral chronic inflammatory pain strongly implicates a role for glia, and local synthesis of proinflammatory cytokines and growth factors. A characteristic feature of CNS inflammation is gliosis, in which inflammatory mediators activate glial cells (e.g. astrocytes and microglia, macrophages and leukocytes) which have been shown to induce and maintain hyperalgesia. In addition, inflammatory pain induces changes in blood-brain barrier (BBB) permeability and alters transport of clinically relevant drugs used to treat pain into the brain. Despite the increasing body of evidence for the involvement of glia in chronic pain and the role of glia in maintaining the BBB, few studies have addressed glial/endothelial interactions and the mechanisms by which glia may regulate the BBB during inflammatory pain. Further studies into the cellular mechanisms of glial/endothelial interactions may identify novel therapeutic targets for reversing chronic inflammatory induced BBB dysfunction and innovate therapies for modulating the severity of chronic inflammatory pain.     

Cannabinoid agonist WIN 55,212-2 prevents the development of paclitaxel-induced peripheral neuropathy in rats. Possible involvement of spinal glial cells

Spinal glial activation contributes to the development and maintenance of chronic pain states, including neuropathic pain of diverse etiologies. Cannabinoid compounds have shown antinociceptive properties in a variety of neuropathic pain models and are emerging as a promising class of drugs to treat neuropathic pain. Thus, the effects of repeated treatment with WIN 55,212-2, a synthetic cannabinoid agonist, were examined throughout the development of paclitaxel-induced peripheral neuropathy. Painful neuropathy was induced in male Wistar rats by intraperitoneal (i.p.) administration of paclitaxel (1mg/kg) on four alternate days. Paclitaxel-treated animals received WIN 55,212-2 (1mg/kg, i.p.) or minocycline (15 mg/kg, i.p.), a microglial inhibitor, daily for 14 days, simultaneous with the antineoplastic. The development of hypersensitive behaviors was assessed on days 1, 7, 14, 21 and 28 following the initial administration of drugs. Both the activation of glial cells (microglia and astrocytes) at day 29 and the time course of proinflammatory cytokine release within the spinal cord were also determined. Similar to minocycline, repeated administration of WIN 55,212-2 prevented the development of thermal hyperalgesia and mechanical allodynia in paclitaxel-treated rats. WIN 55,212-2 treatment also prevented spinal microglial and astrocytic activation evoked by paclitaxel at day 29 and attenuated the early production of spinal proinflammatory cytokines (interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α). Our results confirm changes in the reactivity of glial cells during the development of peripheral neuropathy induced by paclitaxel and support a preventive effect of WIN 55,212-2, probably via glial cells reactivity inactivation, on the development of this neuropathy.     

Inflammation-like glial response in lead-exposed immature rat brain.

Numerous studies on lead (Pb) neurotoxicity have indicated this metal to be a dangerous toxin, particularly during developmental stages of higher organisms. Astrocytes are responsible for sequestration of this metal in brain tissue. Activation of astroglia may often lead to loss of the buffering function and contribute to pathological processes. This phenomenon is accompanied by death of neuronal cells and may be connected with inflammatory events arising from the production of a wide range of cytokines and chemokines. The effects of prolonged exposure to Pb upon glial activation are examined in immature rats to investigate this potential proinflammatory effect. When analyzed at the protein level, glial activation is observed after Pb exposure, as reflected by the increased level of glial fibrillary acidic protein and S-100beta proteins in all parts of the brain examined. These changes are associated with elevation of proinflammatory cytokines. Production of interleukin (IL)-1beta and tumor necrosis factor-alpha is observed in hippocampus, and production of IL-6 is seen in forebrain. The expression of fractalkine is observed in both hippocampus and forebrain but inconsiderably in the cerebellum. In parallel with cytokine expression, signs of synaptic damage in hippocampus are seen after Pb exposure, as indicated by decreased levels of the axonal markers synapsin I and synaptophysin. Obtained results indicate chronic glial activation with coexisting inflammatory and neurodegenerative features as a new mechanism of Pb neurotoxicity in immature rat brain.     

Targeting glia for bone cancer pain

Introduction: Bone cancer pain (BCP) remains to be a clinical challenge with limited pharmaceutical interventions. Therefore, novel therapeutic targets for the management of BCP are in desperate need. Recently, a growing body of evidence has suggested that glial cells may play a pivotal role in the pathogenesis of BCP.

Areas covered: This review summarizes the recent progress in the understanding of glia in BCP and reveals the potential therapeutic targets in glia for BCP treatment.

Expert opinion: Pharmacological interventions inhibiting the activation of glial cells, suppressing glia-derived proinflammatory cytokines, cell surface receptors, and the intracellular signaling pathways may be beneficial for the pain management of advanced cancer patients. However, these pharmacological interventions should not disrupt the normal function of glia cells since they play a vital supportive and protective role in the central nervous system.     

Inhibition of glial inflammatory activation and neurotoxicity by tricyclic antidepressants

Glial activation and neuroinflammatory processes play an important role in the pathogenesis of neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and HIV dementia. Activated glial cells can secrete various proinflammatory cytokines and neurotoxic mediators, which may contribute to neuronal cell death. Inhibition of glial activation may alleviate neurodegeneration under these conditions. In the present study, the antiinflammatory and neuroprotective effects of tricyclic antidepressants were investigated using cultured brain cells as a model. The results showed that clomipramine and imipramine significantly decreased the production of nitric oxide or tumor necrosis factor-alpha (TNF-alpha) in microglia and astrocyte cultures. Clomipramine and imipramine also attenuated the expression of inducible nitric oxide synthase and proinflammatory cytokines such as interleukin-1beta and TNF-alpha at mRNA levels. In addition, clomipramine and imipramine inhibited IkappaB degradation, nuclear translocation of the p65 subunit of NF-kappaB, and phosphorylation of p38 mitogen-activated protein kinase in the lipopolysaccharide-stimulated microglia cells. Moreover, clomipramine and imipramine were neuroprotective as the drugs reduced microglia-mediated neuroblastoma cell death in a microglia/neuron co-culture. Therefore, these results imply that clomipramine and imipramine have antiinflammatory and neuroprotective effects in the central nervous system by modulating glial activation.     

The role of neuroinflammation in neuropathic pain: mechanisms and therapeutic targets

Neuroinflammation is a proinflammatory cytokine-mediated process that can be provoked by systemic tissue injury but it is most often associated with direct injury to the nervous system. It involves neural-immune interactions that activate immune cells, glial cells and neurons and can lead to the debilitating pain state known as neuropathic pain. It occurs most commonly with injury to peripheral nerves and involves axonal injury with Wallerian degeneration mediated by hematogenous macrophages. Therapy is problematic but new trials with anti-cytokine agents, cytokine receptor antibodies, cytokine-signaling inhibitors, and glial and neuron stabilizers provide hope for future success in treating neuropathic pain.