神经病理性疼痛增强HCN2通道在大鼠触液核的表达

本文旨在研究超极化激活环核苷酸门控通道亚型2(hyperpolarization-activated cyclic nucleotide-gated channels subtype2,HCN2)在触液核的分布及其在神经病理性疼痛条件下的表达变化,以期为揭示触液核的生物学功能及神经病理性疼痛的调控机制提供实验依据。以Sprague-Dawley(SD)大鼠为实验动物,用坐骨神经慢性压迫损伤(chronic constriction injury,CCI)法制作神经病理性疼痛模型,用侧脑室注射辣根过氧化物酶标记的霍乱毒素B亚单位复合物(CB-HRP)特异性标记触液核神经元,用热缩足潜伏期及机械缩足阈值作为定量指标研究痛行为,用免疫荧光法及Western blot检测触液核HCN2通道蛋白及c-Fos蛋白的表达量。结果显示,与正常大鼠相比,接受侧脑室CB-HRP注射的大鼠痛阈及触液核HCN2、c-Fos表达均无明显变化;而CCI术后第7、14天,神经病理性疼痛模型大鼠痛阈显著下降,且触液核神经元的HCN2通道蛋白及c-Fos蛋白的表达显著增加。使用HCN2阻断剂ZD7288后,CCI致痛大鼠痛阈显著提高,触液核神经元HCN2通道蛋白及c-Fos蛋白的表达较相应时间点模型组显著降低,以术后第7、14天为明显。以上结果提示,触液核可能参与了神经病理性疼痛的调制,且通过HCN2通道发挥重要作用。     

电压门控钠通道在神经病理性痛中的作用

电压门控钠通道(VGSC)在神经病理性痛的发生和维持中起重要作用。非特异性的通道阻断剂是神经病理性痛的一种治疗手段,但由于可能产生严重的副作用而限制了其使用。最近研究揭示了几种主要在外周感觉神经系统中表达的VGSC的亚型与神经病理性痛密切相关,发展特异性的通道亚型阻断剂将成为治疗神经病理性痛的重要研究方向。     

超极化激活的环核苷酸门控通道（HCN 通道）抑制剂的研究进展

超极化激活的环核苷酸门控通道(HCN通道)有四个亚型,分别为HCN1-4。HCN通道各亚型之间的基本结构相似,在许多组织中均有表达,其中以大脑和心脏组织中表达最为丰富。HCN通道既参与所在组织的正常生理功能,也与所在组织的病理状态密切相关。如神经损伤引起的神经源性疼痛常检测到HCN1通道表达量的增加,肥厚性心肌病和终末期心力衰竭等病理状态下常检测到心室肌细胞HCN4 mRNA及HCN2 mRNA表达增加。鉴于HCN通道与许多疾病密切相关,因此,以其为靶点来治疗相关疾病成为可能,但是由于HCN通道分布广泛,而目前该通道阻滞剂均为非选择性亚型抑制剂,临床应用时不可避免的引起副反应,因此发展选择性HCN通道亚型抑制剂就显得刻不容缓。本文就HCN通道抑制剂的研究发展做进一步探讨。     

HCN2在大鼠外周神经病理性疼痛发生中的作用

目的：初步探讨超极化激活的环核苷酸门控通道2型（HCN2）在外周神经病理性疼痛发生中的作用。方法：将24只健康成年大鼠进行随机分组（n=12）：假手术组（Sham）大鼠仅分离左侧L4、L5脊神经,模型组（SNL）分离脊神经后进行相应的结扎处理,手术7 d后用行为学方法进行模型评价;将造模成功的大鼠进行随机分组（n=6）：①阴性对照组（Saline）,左侧足底注射生理盐水;②阳性对照组（GBPT）,腹腔注射加巴喷丁;③实验组（ZD7288）,左侧足底注射HCN非特异性阻断剂ZD7288。在给药前以及给药后1 h、4 h、24 h、48 h用疼痛行为学实验检测其对神经病理性疼痛的作用;分别取手术前对照组（Control）、假手术组（Sham）和模型组（SNL）大鼠的背根神经节（DRG）（n=6）,利用qPCR和Western blot的方法研究造模前后大鼠DRG内HCN2的表达的变化情况。结果：①成功建立大鼠神经痛模型;②与Saline组比较,GBPT组和ZD7288组在注射1 h后,均能明显的减轻大鼠神经病理性疼痛的症状（P<0.01）,而GBPT组和ZD7288组之间比较则无差异;③与Control组和Sham组相比较,SNL组大鼠DRG内的HCN2 mRNA表达量明显增加（P<0.01）;与Control组和Sham组相比较,SNL组大鼠DRG内的HCN2通道蛋白表达量显著增加（P<0.05）。结论：HCN2参与外周神经病理性疼痛的发生,并有可能成为治疗神经病理性疼痛一个潜在的新靶点。     

超极化激活环核苷酸门控阳离子通道(HCN)研究进展

HCN是超极化激活环核苷酸门控阳离子通道,其激活后产生If/Ih电流,能被ZD7288和Cs+特异性阻断.该通道有4个亚型,具有稳定细胞膜电位、参与心脏和神经节律调节、参与树突整合,以及调节神经递质释放等生理功能.近期实验中发现豚鼠膀胱ICC上存在Ih电流,其功能特点值得进一步研究和探讨.     

HCN通道:生物学特性及疼痛相关作用

脊椎动物的超极化激活环核苷酸门控通道(hyperpolarization-activated cyclic nucleotide-gated channels,HCN通道)具有反向电压依赖性,其开放依赖细胞表面的超极化。HCN在机体各组织的分布和数量及开放状态存在差异。HCN通道的开放受到cAMP及其它物质或信号传导通路直接或者间接的调控。HCN及其介导的Ih/If电流可以影响细胞膜静息电位,控制神经元兴奋性、突触电位和突触传递并在调节心律等方面起到重要作用,并且参与了疼痛等生理或病理过程的调控。部分药物可以通过对HCN通道的作用治疗疼痛等相关疾病。本文将从HCN通道的结构、分布、调控、在疼痛及其它相关疾病中起到的作用等方面对近年来HCN通道研究的新发现进行回顾和综述。     

Fractalkine及其受体CX3CR1与神经病理性疼痛

神经病理性疼痛是由于神经系统的损伤和炎症引起的,发病率日益增高,但是根本机制仍然不清楚。动物实验表明细胞因子和趋化因子参与神经病理性疼痛的发生。作为唯一的CX3C亚族的膜结合型趋化因子Fractalkine（Fkn）在神经病理性疼痛发病机制中的作用日益受到关注,有望成为神经病理性疼痛治疗的新靶点。Fkn及其受体有其特殊结构和功能作用,本文就其参与神经病理性疼痛的可能机制,调节吗啡的效应作一综述。     

钠离子通道NaV1.7与神经病理性疼痛

钠通道NaV1.7是电压门控性钠通道的亚型之一。大多数钠离子通道NaV1.7表达在背根神经节(DRG)小C纤维的伤害性感受器上,具有缓慢开放和缓慢关闭失活的特点。它能够产生大量的斜坡电流,降低感觉神经元中动作电位产生的阈值,放大外来小的缓慢的去极化斜坡电流,从而增加神经元兴奋性,对疼痛的产生、传递、调节具有关键性作用。随着遗传学研究的不断深入,钠离子通道NaV1.7的功能获得性突变和功能缺失性突变,使其成为了新型镇痛疗法中一个的特别有吸引力的药物靶点,受到人们的广泛关注。而研究发现,NaV1.7通道在不同因素引起的神经病理性疼痛中通过不同途径提高神经元兴奋性,参与神经病理性疼痛,给NaV1.7选择性抑制剂研发带来了巨大阻碍。目前,虽然已有的NaV1.7选择性抑制剂具备有效镇痛作用,且无明显副作用或成瘾问题,但寻找NaV1.7选择性配体极其困难。此外,现有的NaV1.7选择性抑制剂也因神经病理性疼痛类型的不同在抑制效力、靶向性、安全性以及可行性等方面存在差异。提示寻找NaV1.7通道作用于不同神经病理性疼痛的普遍机制或NaV1.7通道特有的受体结合位点,可能是未来NaV1.7选择性抑制剂研发的主要方向。本文就NaV1.7通道在不同因素引起的神经病理性疼痛中的主要作用进行简要综述。     

肠道菌群调控慢性疼痛机制的研究进展

近年来,肠道菌群与肠-脑轴的相互作用逐渐被认识,肠道菌群参与调控神经系统相关疾病的机制也日益被关注,其中肠道菌群可参与调控多种慢性疼痛,包括内脏痛、炎性痛、神经病理性疼痛和头痛等。肠道菌群本身的成分以及其代谢产物和副产物会通过调控多种细胞信号通路及神经递质干预慢性疼痛的发生和发展。本文对已发表的肠道菌群调控慢性疼痛的相关研究进行了广泛检索及总结,并在此基础上综述肠道菌群参与慢性疼痛的机制,以期为研发通过调控肠道菌群而发挥镇痛作用的靶点药物提供理论基础。     

膜超极化激活离子通道及其靶向抗癫痫药物研究进展

癫痫是一种较为常见的神经系统疾病,主要以大量神经元同步异常放电为特征。目前普遍认为,神经元或神经网络兴奋性和抑制性 电信号传输的失衡,是癫痫发病的最根本原因。现有的抗癫痫药物主要以钠离子通道、钙离子通道、钾离子通道、谷氨酸受体和γ-氨基丁 酸离子通道为靶点,但接受这些药物治疗后,仍有近1/3的病人无法控制癫痫发作。因此,抗癫痫药物的研发亟需新靶点和新思路。许多 研究证据表明,膜超极化激活离子通道的基因突变可以导致遗传型癫痫的发作,且在脑部损伤后,膜超极化激活离子通道会发生表达水平、 通道生物物理学性质及通道亚基构成的改变,从而增加神经元和神经网络兴奋性,促使癫痫发病。故近年来,膜超极化激活离子通道及其 靶向抗癫痫药物研究引起人们广泛关注。综述膜超极化激活离子通道与癫痫发病之间的关系,并探讨以膜超极化激活离子通道为靶点进行 抗癫痫药物开发和治疗的可行性。     

Characteristics of HCN Channels and Their Participation in Neuropathic Pain

Neuropathic pain is induced by the injury to nervous systems and characterized by hyperalgesia, allodynia and spontaneous pain. The underlying mechanisms include peripheral and central sensitization resulted from neuronal hyperexcitability. A number of ion channels are considered to contribute to the neuronal hyperexcitability. Here, we particularly concentrate on an interesting ion channel, hyperpolarization-activated cyclic nucleotide gated (HCN) channels. We overview its biophysical properties, physiological functions, followed by focusing on the current progress in the study of its role in the development of neuropathic pain. We attempt to provide a comprehensive review of the potential valuable target, HCN channels, in the treatment of neuropathic pain. Special issue article in honor of Dr. Ji-Sheng Han. Yu-Qiu Jiang, Qian Sun, and Hui-Yin Tu—contributed equally to this paper.     

miR-194 relieve neuropathic pain and prevent neuroinflammation via targeting FOXA1

The emerging role of microRNAs (miRNAs) have been deeply explored in multiple diseases including neuropathic pain. miR-194 was widely reported to be a tumor suppressor and was related to the inflammatory response. The critical role of neuroinflammation on neuropathic pain leads to a thinking about the relationship between miR-194 and neuropathic pain. However, the function of miR-194 in neuropathic pain remains unknown. This study was aimed to explore the relationship between miR-194 and neuropathic pain progression by chronic sciatic nerve injury (CCI). miR-194 abnormally downregulated in the CCI model rat and its overexpression significantly alleviates neuroinflammation in vivo. We predict Forkhead box protein A1 (FOXA1) as a direct target of miR-194, whose restoration can markedly reverse the effects of miR-194 on neuropathic pain. Overall, our study demonstrated a novel mechanism of neuropathic pain progression that miR-194 alleviates neuropathic pain via targeting FOXA1 and preventing neuroinflammation by downregulating inflammatory cytokines containing cyclooxygenase 2, interleukin 6 (IL-6), and IL-10 in vivo, which can be reversed by the overexpression of FOXA1.     

Reduction in the mechanonociceptive response by intrathecal administration of glycine and related compounds

We have previously reported that enhanced glycine release is produced by epidural spinal cord stimulation, a clinical method for treating neuropathic pain. Our current hypothesis is that glycine administered intrathecally reduces neuropathic pain as measured by the Randall-Selitto method. Neuropathic rats created by unilateral partial ligation of the sciatic nerve were treated with intrathecal infusion of glycine, strychnine, MK-801, or 5,7-DKA at 0.1 μmol, or artificial CSF for 2 hours at a rate of 10 μl/min. Force required to produce the pain response was significantly increased after glycine administration and reduced using strychnine, a specific glycine receptor (Gly 1) antagonist. Strychnine blocked the response to glycine when infused together. Administration of the non-specific NMDA receptor MK-801 antagonist and 5,7-DKA, a specific glycine-NMDA receptor (Gly 2) antagonist, however, failed to block the response to glycine. Our results provide evidence for the use of glycine and related compounds to treat neuropathic pain.     

P2X7受体在病理性疼痛中的研究进展

病理性疼痛主要包括组织损伤或炎症引起的炎症痛、神经系统损伤或疾病引起的神经病理性疼痛和恶性肿瘤及治疗引起的癌症痛三大类。病理性疼痛对常规的镇痛药物反应不理想,迫切需要寻找新的对病理性疼痛更有效和更特异的治疗手段。P2X7受体作为离子通道型嘌呤能受体,在炎症痛、神经病理性疼痛和癌症痛中都具有重要作用。靶向P2X7受体的新药物将为病理性疼痛的治疗带来新的希望。该文综述了P2X7受体在三类病理性疼痛中的研究进展。     

Evidence for lysophosphatidic acid 1 receptor signaling in the early phase of neuropathic pain mechanisms in experiments using Ki-16425, a lysophosphatidic acid 1 receptor antagonist

Lysophosphatidic acid is a bioactive lipid mediator with neuronal activities. We previously reported a crucial role for lysophosphatidic acid 1 receptor-mediated signaling in neuropathic pain mechanisms. Intrathecal administration of lysophosphatidic acid (1 nmol) induced abnormal pain behaviors, such as thermal hyperalgesia, mechanical allodynia, A-fiber hypersensitization, and C-fiber hyposensitization, all of which were also observed in partial sciatic nerve injury-induced neuropathic pain. Ki-16425 (30 mg/kg, i.p.), a lysophosphatidic acid 1 receptor antagonist, completely blocked lysophosphatidic acid-induced neuropathic pain-like behaviors, when administered 30 min but not 90 min before lysophosphatidic acid injection, suggesting that Ki-16425 is a short-lived inhibitor. The blockade of nerve injury-induced neuropathic pain by Ki-16425 was maximum as late as 3 h after the injury but not after this critical period. The administration of Ki-16425 at 3 h but not at 6 h after injury also blocked neurochemical changes, including up-regulation of voltage-gated calcium channel α₂δ-1 subunit expression in dorsal root ganglion and reduction of substance P expression in the spinal dorsal horn. All of these results using Ki-16425 suggest that lysophosphatidic acid 1 receptor-mediated signaling which underlies the development of neuropathic pain works at an early stage of the critical period after nerve injury.     

Markedly attenuated acute and chronic pain responses in mice lacking adenylyl cyclase-5

Chronic inflammatory and neuropathic pain is often difficult to manage using conventional remedies. The underlying mechanisms and therapeutic strategies required for the management of chronic pain need to be urgently established. The cyclic AMP (cAMP) second messenger system has been implicated in the mechanism of nociception, and the inhibition of the cAMP pathway by blocking the activities of adenylyl cyclase (AC) and protein kinase A has been found to prevent chronic pain in animal models. However, little is known regarding which of the 10 known isoforms of AC are involved in nociceptive pathways. Therefore, we investigated the potential pronociceptive function of AC5 in nociception using recently developed AC5 knockout mice (AC5-/-). We found that AC5-/- mice show markedly attenuated pain-like responses in acute thermal and mechanical pain tests as compared with the wildtype control. Also, AC5-/- mice display hypoalgesic responses to inflammatory pain induced by subcutaneous formalin injection into hindpaws, and to non-inflammatory and inflammatory visceral pain induced by injecting magnesium sulfate or acetic acid into the abdomen. Moreover, AC5-/- mice show strongly suppressed mechanical and thermal allodynia in two nerve injury-induced neuropathic pain models. These results suggest that AC5 is essential for acute and chronic pain, and that AC5 knockout mice provide a useful model for the evaluation of the pathophysiological mechanisms of pain.     

BK(Ca) channel agonist NS1619 and Kv channel antagonist 4-AP on the facial mechanical pain threshold in a rat model of chronic constriction injury of the infraorbital nerve

Trigeminal neuralgia is a paroxysmal disorder with severely disabling facial pain and thus continues to be a real therapeutic challenge. At present there are few effective drugs for treatment of this pain. The present study was aimed to explore the involvement of BK(Ca) channels and Kv channels in the mechanical allodynia in a rat model of trigeminal neuropathic pain. Here the effectiveness of drug target injection at the trigeminal ganglion through the infraorbital foramen was first evaluated by immunofluorescence and animal behavior test. Trigeminal neuropathic pain model was established by chronic constriction injury of the infraorbital nerve (ION-CCI) in rats. BK(Ca) channel agonist and Kv channel antagonist were administered into the trigeminal ganglion in ION-CCI rats and sham rats by the above target injection method, and the facial mechanical pain threshold was measured. The results showed that the drug could accurately reach the trigeminal ganglion by target injection which was more effective than that by the normal injection around infraorbital foramen. Rats suffered significant mechanical allodynia in the whisker pad of the operated side from 6 d to 42 d after ION-CCI. BK(Ca) channel agonist NS1619 significantly and dose-dependently attenuated the facial mechanical allodynia and increased the facial mechanical pain threshold in ION-CCI rats 15 d after operation. Kv antagonist 4-AP was able to reduce the threshold in ION-CCI rats when facial mechanical threshold was partly recovered and relatively stable on the 35th day after operation. These results suggest that BK(Ca) channel agonist NS1619 and Kv channel antagonist 4-AP can significantly affect the rats' facial mechanical pain threshold after ION-CCI. Activation of BK(Ca) channels may be related to the depression of the primary afferent neurons in trigeminal neuropathic pain pathways. Activation of Kv channels may exert a tonic inhibition on the trigeminal neuropathic pain.     

ARA 290 relieves pathophysiological pain by targeting TRPV1 channel: Integration between immune system and nociception

ARA 290 is an erythropoietin-derived polypeptide that possesses analgesic and tissue protective effect in many diseases such as diabetes and cancer. The analgesic effect of ARA 290 is mediated by its anti-inflammatory and immunomodulatory functions, or more specifically, by targeting the innate repair receptor (IRR) to down-regulate inflammation to alleviate neuropathic pain. However, whether other mechanisms or pathways are involved in ARA 290-mediated analgesic effect remains elusive. In this study, we are particularly interested in whether ARA 290 could directly target peripheral nociceptors by blocking or influencing receptors in pain sensation. Using calcium imaging, cell culture and behavioral tests, we demonstrated that ARA 290 was able to specifically inhibit TRPV1 channel activity, and relieve the mechanical hypersensitivity induced by capsaicin. Our study suggested that ARA 290 could potentially function as a novel antagonist for TRPV1 channel. This finding would not only contribute to the development of new pain treatment using ARA 290, but also help to improve our understanding of the integration between the immune system and the peripheral nervous system.