癌痛的分子机理研究进展

疼痛是肿瘤患者的常见并发症。癌痛的产生不同于炎性痛和神经病理性疼痛。动物模型的构建能帮助我们更好地了解癌痛的分子调控机制。随着对癌痛机制的进一步研究,未来针对性的靶点镇痛治疗指日可待。本文就研究癌痛的动物模型及癌痛产生的相关分子机制等方面的进展进行综述。     

综述与专论: 内脏痛实验动物模型的研究进展

内脏痛是内脏器官受到机械性牵拉、炎症、痉挛、应激和缺血等刺激所致的疼痛，是一种临床上常见病症。与躯体痛相比，内脏痛的产生、维持和调控机制更为复杂，因此是目前疼痛基础研究领域中的重点和难点之一。建立符合临床内脏疾病病理生理学特征的实验动物模型对研究内脏痛的产生、维持、调控机制及筛选相关内脏疾病的治疗药物具有重要意义。目前内脏痛动物模型主要按照造模刺激方式进行分类，分为炎性内脏痛模型、电刺激性内脏痛模型、机械扩张性内脏痛模型及缺血性内脏痛模型等，且每种动物模型具有不同特点。本文就近年来内脏痛基础研究中常用的实验动物模型的制备及特点做一简要综述，以期为研究者选择合适的内脏痛动物模型提供参考，为更深入研究内脏痛的复杂机制及筛选相关治疗药物奠定基础。     

神经病理性疼痛研究进展

神经病理胜疼痛是指神经系统的损伤或功能障碍引起的疼痛,占到了各类慢性疼痛的30%以上。第四军医大学完成的—项研究成果成功揭示了神经病理性痛的发生机制,创建两种能够分别模拟神经病理性痛不同临床表现的动物模型为研究神经病理性痛和制定治疗策略奠定了基础。     

周围神经病损引起慢性痛的形态学和生理功能改变

周围神经受损后可导致痛觉过敏、感觉倒错、烧灼性痛等感觉障碍。本文主要对目前国内外普遍采用的、用于研究慢性神经病损性疼痛机制的两种动物模型进行综述,着重介绍神经开矿学和功能的改变。     

外周神经损伤引起的神经病理性痛：对神经损伤 的一种适应不良反应

外周神经损伤可引起对神经系统的一种适应不良反应,其产生神经病理性痛的主要特点为痛觉增敏和异常疼痛。目前文献报道多种机制涉及此反应,包括离子通道改变引起的异常放电、突触易化、多种轴突水平抑制作用缺失导致的中枢敏化、神经元细胞的凋亡以及异常的突触连接等结构的改变,另外神经损伤引起的神经免疫之间的相互作用在神经病理性痛的持续性发展中发挥着不可替代的作用。了解外周神经损伤引起的神经病理性的发病机制将对我们寻找治疗靶点和治疗策略提供坚实的理论基础。     

中脑导水管周围灰质电刺激与丘脑电刺激对大鼠伤害感知行为的差异调节（英文）

深部脑刺激是一种广泛用于治疗中枢神经及精神疾病的功能型手术疗法。深部脑刺激在临床应用于疼痛治疗起源于半个多世纪以前,能够有效治疗多种类型的顽固疼痛,然而其作用机制尚不清楚。为了进一步探索其神经机制,首先需要建立合适的深部脑刺激治疗疼痛的动物模型。本研究在大鼠的中脑导水管周围灰质腹外侧区(ventrolateral periaqueductal gray,vl PAG)或丘脑腹后外侧核(ventral posterior lateral nucleus,VPL)埋置刺激电极,研究深部脑刺激对正常大鼠急性痛、完全弗式佐剂(complete Freund’s adjuvant,CFA)注射引起的慢性炎症痛大鼠模型以及脊神经结扎(spinal nerve ligation,SNL)手术引起神经病理痛大鼠模型的镇痛效果。主要结果如下:(1)在正常大鼠中,单侧vl PAG刺激能够显著提高双侧足底的热辐射痛阈,即产生显著的双侧镇痛作用;(2)在CFA建立的慢性炎症痛模型中,对侧vl PAG刺激和VPL刺激都能够显著提高CFA侧足底的热辐射痛阈,即产生显著的镇痛作用;(3)在SNL手术引发的慢性神经源性痛模型中,对侧VPL刺激能够显著提高SNL侧足底的机械痛阈,而vl PAG刺激对SNL引发的触诱发痛没有影响。以上结果提示,PAG刺激对于急性痛以及慢性炎症痛有着较好的镇痛效果,而VPL刺激更适合慢性炎症痛和慢性神经病理痛的镇痛研究。     

活性氧在脊髓损伤性中枢疼痛敏化中作用机制的研究进展

活性氧是指氧的某些代谢产物和一些反应的含氧产物,研究证实脊髓损伤后继发产生的活性氧与中枢疼痛敏化关系密切。它可能通过激活兴奋性氨基酸受体,继而激活背角神经元中参与敏化的第二信使系统发挥作用,亦与胶质细胞活化和细胞因子、神经营养因子释放有关。本文对活性氧诱发脊髓损伤性中枢疼痛敏化的作用机制作一综述。     

T型钙通道在神经病理性痛模型中介导疼痛的研究进展

神经病理痛是临床上常见病症,其发病机制尚不清楚,目前尚无有效的治疗手段,其慢性神经病理痛持续时间长,故其研究成为疼痛领域的热点和重点。近年来发现T型钙通道在神经病理性疼痛中起到了关键性的作用。本文将近年T型钙通道在神经病理性痛模型中介导疼痛的机制研究进展加以综述。     

TRPV1:一种同时参与慢性痛外周敏化和疼痛中枢调制的重要分子

慢性痛是困扰临床的一大顽疾,关于慢性痛机制的研究和新型镇痛药物的研发具有重要意义。十多年来,本研究组围绕慢性痛外周敏化形成的关键分子——瞬时受体电位香草酸亚型1(transient receptor potential vanilloid type 1,TRPV1),对其敏化和膜定位机制进行了系列研究,揭示了蛋白激酶PKD1(protein kinase D1)、Cdk5(cyclin-dependent kinase 5)和LIMK(LIM-motif containing kinase)在炎症诱发热痛敏中的作用及其对TRPV1的功能调控,并据此开发出了一系列具有镇痛作用的Tat穿膜肽。本综述还围绕研究组近期工作所揭示的参与痛感觉和痛情绪相互作用的关键脑区——前额叶皮质的前边缘皮质亚区,对TRPV1在其中的可能作用进行了探讨。此外本综述也对研究组在改进TRPV1靶向药物,提高其镇痛疗效,降低副作用方面的工作进行了简要总结和回顾。     

下行易化系统及其参与神经病理痛的机制

神经病理痛是指由中枢或外周神经系统损伤或疾病引起的疼痛综合征.神经病理痛是临床上常见的一种疾病,但是其发病机制不甚清楚,临床上也缺乏有效的治疗手段.近年来的研究除了集中于痛觉的上行传导及中枢机制,以及痛觉的下行抑制之外,也证明下行易化系统激活参与神经病理痛的发病机制.本文拟对此进行综述,希望为治疗神经病理痛提供新思路.     

Mechanisms of neuropathic pain

Neuropathic pain refers to pain that originates from pathology of the nervous system. Diabetes, infection (herpes zoster), nerve compression, nerve trauma, "channelopathies," and autoimmune disease are examples of diseases that may cause neuropathic pain. The development of both animal models and newer pharmacological strategies has led to an explosion of interest in the underlying mechanisms. Neuropathic pain reflects both peripheral and central sensitization mechanisms. Abnormal signals arise not only from injured axons but also from the intact nociceptors that share the innervation territory of the injured nerve. This review focuses on how both human studies and animal models are helping to elucidate the mechanisms underlying these surprisingly common disorders. The rapid gain in knowledge about abnormal signaling promises breakthroughs in the treatment of these often debilitating disorders.     

Functional imaging of the human trigeminal system: opportunities for new insights into pain processing in health and disease

Peripheral inflammation or nerve damage result in changes in nervous system function, and may be a source of chronic pain. A number of animal studies have indicated that central neural plasticity, including sensitization of neurons within the spinal cord and brain, is part of the response to nervous system insult, and can result in the appearance of altered sensation, including pain. It cannot be assumed, however, that data obtained from animal models unambiguously reflects CNS changes that occur in humans. Currently, the only noninvasive approach to determining objective changes in neural processing and responsiveness within the CNS in humans is the use of functional imaging techniques. It is now possible to use functional magnetic resonance imaging (fMRI) to measure CNS activation in the trigeminal ganglion, spinal trigeminal nucleus, the thalamus, and the somatosensory cortex in healthy volunteers, in a surrogate model of hyperalgesia, and in patients with trigeminal pain. By offering a window into the temporal and functional changes that occur in the damaged nervous system in humans, fMRI can provide both insight into the mechanisms of normal and pathological pain and, potentially, an objective method for measuring altered sensation. These advances are likely to contribute greatly to the diagnosis and treatment of clinical pain conditions affecting the trigeminal system (e.g., neuropathic pain, migraine).     

Changes in response properties of nociceptive dorsal horn neurons in a murine model of cancer pain

Pain associated with cancer that metastasizes to bone is often severe and debilitating. A better understanding of the neural mechanisms that mediate cancer pain is needed for the development of more effective treatments. In this study, we used an established model of cancer pain to characterize changes in response properties of dorsal horn neurons. Fibrosarcoma cells were implanted into and around the calcaneus bone in mice and extracellular electrophysiological recordings were made from wide dynamic range (WDR) and high threshold (HT) dorsal horn neurons. Responses of WDR and HT neurons evoked by mechanical, heat, and cold stimuli applied to the plantar surface of the hind paw were compared between tumor bearing mice and control mice. Mice exhibited hyperalgesia to mechanical and heat stimuli applied to their tumor-bearing hind paw. WDR neurons in tumor-beating mice exhibited an increase in spontaneous activity, and enhanced responses to mechanical, heat, and cold stimuli as compared to controls. Our findings show that sensitization of WDR neurons, but not HT neurons, contributes to tumor-evoked hyperalgesia.     

Plasticity of pain signaling: role of neurotrophic factors exemplified by acid-induced pain

Acute noxious stimuli activate a specialized neuronal detection system that generates sensations of pain and, generally, adaptive behavioral responses. More persistent noxious stimuli notably those associated with some chronic injuries and disease states not only activate the pain-signaling system but also dramatically alter its properties so that weak stimuli produce pain. These hyperalgesic states arise from at least two distinct broad classes of mechanisms. These are peripheral and central sensitization associated with increased responsiveness of peripheral nociceptor terminals and dorsal horn neurons, respectively. Here we review the key features of these sensitized states and discuss the role of one neurotrophic factor, nerve growth factor, as a peripheral mediator of sensitization and of another factor, brain-derived neurotrophic factor, as a mediator of central sensitization. We use as a specific example the pain induced by acid stimuli. We review the neurobiology of such pain states, and discuss how acid stimuli both initiate sensitization and how the neuronal processing of acid stimuli is subject to sensitization.     

Animal models of cancer pain

Modern cancer therapies have significantly increased patient survival rates in both human and veterinary medicine. Since cancer patients live longer they now face new challenges resulting from severe, chronic tumor-induced pain. Unrelieved cancer pain significantly decreases the quality of life of such patients; thus the goal of pain management is to not only to alleviate pain, but also to maintain the patient's physiological and psychological well-being. The major impediment for developing new treatments for cancer pain has been our limited knowledge of the basic mechanisms that drive cancer pain and the lack of adequate animal cancer pain models to study the molecular, biochemical and neurobiological pathways that generate and maintain cancer pain. However this situation has recently changed with the recent development of several novel animal models of cancer pain. This review will focus on describing these animal models, many of them in rodents, and reviewing some of the recent information gained from the use of these models to investigate the basic mechanims that underlie the development and maintenance of cancer pain. Animal models of cancer pain can be divided into the following five categories: bone cancer pain models, non-bone cancer pain models, cancer invasion pain models, cancer chemotherapeutic-induced peripheral neuropathy models, and spontaneous occurring cancer pain models. These models will be important not only for enhancing our knowledge of how cancer pain is generated, but more importantly for the development of novel therapeutic regimes to treat cancer pain in both domestic animals and humans.     

Behavioral, medical imaging and histopathological features of a new rat model of bone cancer pain

Pre-clinical bone cancer pain models mimicking the human condition are required to respond to clinical realities. Breast or prostate cancer patients coping with bone metastases experience intractable pain, which affects their quality of life. Advanced monitoring is thus required to clarify bone cancer pain mechanisms and refine treatments. In our model of rat femoral mammary carcinoma MRMT-1 cell implantation, pain onset and tumor growth were monitored for 21 days. The surgical procedure performed without arthrotomy allowed recording of incidental pain in free-moving rats. Along with the gradual development of mechanical allodynia and hyperalgesia, behavioral signs of ambulatory pain were detected at day 14 by using a dynamic weight-bearing apparatus. Osteopenia was revealed from day 14 concomitantly with disorganization of the trabecular architecture (μCT). Bone metastases were visualized as early as day 8 by MRI (T(1)-Gd-DTPA) before pain detection. PET (Na(18)F) co-registration revealed intra-osseous activity, as determined by anatomical superimposition over MRI in accordance with osteoclastic hyperactivity (TRAP staining). Pain and bone destruction were aggravated with time. Bone remodeling was accompanied by c-Fos (spinal) and ATF3 (DRG) neuronal activation, sustained by astrocyte (GFAP) and microglia (Iba1) reactivity in lumbar spinal cord. Our animal model demonstrates the importance of simultaneously recording pain and tumor progression and will allow us to better characterize therapeutic strategies in the future.     

Understanding the signaling and transmission of visceral nociceptive events

Visceral pain can be considered as part of the defense reactions of the body against harmful stimuli, particularly of those that impinge on the mucosal lining of hollow organs. It is a problem of considerable clinical relevance, and its neurobiological mechanisms differ from those of somatic nociceptive or neuropathic pain. Much progress had been made in recent years in the understanding of the functional properties of the visceral nociceptors that trigger pain states, their molecular mechanisms of activation and sensitization and on their central actions. Some molecular targets have been identified as key players in the activation and sensitization of visceral nociceptors, notably ASICs, TTX-resistant Na channels and the TRPV1 receptor. Some nonneural elements of visceral organs, such as the urothelium have been shown to play active roles in the transduction of visceral sensory events by mechanisms involving ATP release by the urothelial cells. Certain well-known neurotransmitters, such as the tachykinin family of neuropeptides, likely play an important role in the peripheral and central activation of visceral nociceptive afferents and in the generation of visceral hyperalgesia. This article reviews current evidence on the mechanisms of activation and sensitization of visceral nociceptive afferents and on their role in the triggering and maintenance of clinically relevant visceral pain states.     

Neural mechanisms of hyperalgesia.

Hyperalgesia, or enhanced sensitivity to pain, is a symptom often associated with inflammation, nerve injury and various diseases. Although hyperalgesia appears to be mediated by sensitization of peripheral and central pain-signalling neurons, underlying mechanisms of sensitization are not well understood. Recent contributions to our knowledge of the mechanisms underlying hyperalgesia and sensitization are reviewed.