Current perspectives on the modulation of thermo-TRP channels: new advances and therapeutic implications

The thermo transient receptor potential (TRP) ion channels, a recently discovered family of ion channels activated by temperature, are expressed in primary sensory nerve terminals, where they provide information regarding thermal changes in the environment. Six thermo-TRPs have been characterized to date: TRPV1–4, which respond to different levels of warmth and heat, and TRPM8 and TRPA1, which respond to cool temperatures. We review the current state of knowledge of thermo-TRPs, and of the modulation of their thermal thresholds by a range of inflammatory mediators. Blockers of these channels are likely to have therapeutic uses as novel analgesics but may also cause unacceptable side effects. Controlling the modulation of thermo-TRPs by inflammatory mediators may be a useful alternative strategy in developing novel analgesics.     

Artemin和基质金属蛋白酶2在食管鳞癌中的表达及其临床意义

目的 通过检测artemin和基质金属酶2(MMP2)在食管鳞癌中的表达水平,探讨其与食管癌的生长、浸润及转移之间的关系.方法 采用免疫组化的方法,对126例食管鳞癌患者手术切除的标本进行artemin和MMP2检测,并分析其临床病理意义.结果 Artemin与患者的TNM分期及淋巴结转移有密切的关系(P<0.05),与病变的分化程度、病变长度无明显的关系(P＞0.05).而且artemin与MMP2的表达呈正相关(r=0.551,P<0.01).结论 Artemin的表达与食管癌的病理分期、淋巴结转移和病变的分化程度有密切的关系,artemin与MMP2表达呈正相关,可以作为临床评估食管癌进展和预后的指标.     

GDNF家族成员artemin在大鼠视网膜神经节细胞中的表达及其功能

目的观察胶质细胞系源性神经营养因子（GDNF）家族成员artemin在正常大鼠视网膜神经节细胞（RGCs）中的分布、表达及其功能。方法体外培养出生1～3d SD乳鼠的视网膜神经上皮细胞,免疫荧光染色检测RGCs中artemin的定位及表达,实时定量聚合酶链反应（real—time PCR）对RGCs中artemin进行定量检测。并用40mmol／L葡萄糖处理细胞12h后,再进行上述检测,观察高糖对于RGCs中artemin表达的影响。结果免疫荧光的结果证实了培养的RGCs出现Thy1．1抗体阳性的红色荧光,且多重荧光标记显示RGCs同时存在显示绿色荧光的artelnin抗体和红色荧光的Thy1．1抗体,表明artemin在RGCs中有分布。正常对照组中Thy1．1抗体阳性的细胞为（442±9）个／高倍视野,而40mmol／L高糖培养组中为（263±7）个／高倍视野,差异有统计学意义（P〈0．05）。Real—time PCR对大鼠RGCs中artemin的mRNA水平进行定量分析,40mmol／L葡萄糖处理视网膜神经细胞12h后,artemin在视网膜神经细胞及RGCs的表达明显下降（P〈0．05）。结论研究发现在原代培养的大鼠视网膜神经细胞及RGCs巾均有artemin的表达,并且在高糖作用下表达下降,为进一步研究artemin对受损RGCs的保护作用提供了思路。     

Artemin在食管癌中表达作用的研究﹡

目的：探讨 Artemin（ATRN）在食管癌中的表达及作用。方法： 采用免疫组化和 real-time PCR 方法检测ATRN 在食管癌组织 126 例、癌旁组织 126 例和正常组织 21 例中的表达水平;应用 siRNA 技术在食管癌 TE11 细胞系中研究ATRN 表达及对肿瘤细胞的凋亡影响。结果： 126 例食管癌中ATRN 的阳性表达率为73.81% （93/126） ,癌旁组织的阳性表达率为44.44% （56/126） ; 21 例正常食管组织中的ATRN 阳性表达率为14.29% （3/21）,正常食管组织与食管癌组织及癌旁组织比较差异均有统计学意义 （字2分别为 32.89、 23.15, 均 P 约 0.01） ; TE11-siRNA 细胞系 ATRN 的mRNA 和蛋白表达水平均低于 TE11-CK细胞系中相应的表达水平。siRNA 抑制食管癌细胞中 ATRN 的表达后, 促进了 TE11 细胞的凋亡。结论： ATRN 与食管癌的生物学行为有关。     

Artemin promotes functional long-distance axonal regeneration to the brainstem after dorsal root crush

Recovery after a spinal cord injury often requires that axons restore synaptic connectivity with denervated targets several centimeters from the site of injury. Here we report that systemic artemin (ARTN) treatment promotes the regeneration of sensory axons to the brainstem after brachial dorsal root crush in adult rats. ARTN not only stimulates robust regeneration of large, myelinated sensory axons to the brainstem, but also promotes functional reinnervation of the appropriate target region, the cuneate nucleus. ARTN signals primarily through the RET tyrosine kinase, an interaction that requires the nonsignaling coreceptor GDNF family receptor (GFRα3). Previous studies reported limited GFRα3 expression on large sensory neurons, but our findings demonstrate that ARTN promotes robust regeneration of large, myelinated sensory afferents. Using a cell sorting technique, we demonstrate that GFRα3 expression is similar in myelinated and unmyelinated adult sensory neurons, suggesting that ARTN likely induces long-distance regeneration by binding GFRα3 and RET. Although ARTN is delivered for just 2 wk, regeneration to the brainstem requires more than 3 mo, suggesting that brief trophic support may initiate intrinsic growth programs that remain active until targets are reached. Given its ability to promote targeted functional regeneration to the brainstem, ARTN may represent a promising therapy for restoring sensory function after spinal cord injury.Spinal cord (SC) injury results in permanent paresis and paralysis, owing in large part to the failure of axons to regenerate. In the adult SC, axons do not regenerate because of myelin- and injury-associated inhibitory barriers and a limited intrinsic regenerative ability (1). Although there has been some success in removing extrinsic barriers and providing neurotrophic factors to promote functional regeneration over short distances (2–4), meaningful functional recovery requires that damaged axons regenerate and reconnect with their original targets, often centimeters away from the lesion. Studies in which damaged sensory axons were induced to regenerate to the brainstem have failed to show reestablishment of synapses (5). These findings cast doubt on whether sensory axons can regenerate functionally to the brainstem.Dorsal root (DR) crush provides a useful model for studying long-distance axon regeneration without affecting the architecture of the SC. Fine touch and proprioceptive neurons with cell bodies in the DR ganglion (DRG) provide monosynaptic input to neurons in the dorsal column nuclei. These neurons can be traced using transganglionic labeling methods and are easily studied electrophysiologically, making this an ideal injury model for investigating functional regeneration from the brachial SC to the brainstem.Previous studies demonstrated that a 2-wk systemic treatment with the neurotrophic factor artemin (ARTN) promotes topographically specific regeneration of both myelinated and unmyelinated sensory axons into the SC at 1 mo after DR crush (3, 6). This results in persistent recovery of simple behavioral tasks and of electrophysiological function in the SC. In addition, Wang et al. (3) provided evidence that ARTN might promote sensory axon regeneration to the brainstem, although the extent, functionality, and mechanism of regeneration to distant targets remain unknown.The major mechanism of ARTN action is via binding to a nonsignaling coreceptor, GDNF family receptor (GFRα3), and the RET receptor tyrosine kinase, forming a complex that activates intracellular signaling cascades (7). Earlier studies suggested that GFRα3 is expressed primarily in small sensory neurons, with limited expression in large neurons (8, 9); thus, how ARTN promotes robust regeneration of large sensory axons is unclear.In this paper, we report that ARTN induces functional regeneration of myelinated sensory axons across several centimeters to the brainstem. Over several months after DR crush, sensory axons in ARTN-treated rats regenerate to the cuneate nucleus (CN), where they reestablish functional synapses. Given this evidence of large-fiber regeneration, we investigated whether myelinated sensory neurons express GFRα3. In contrast to earlier studies, we found that GFRα3 is expressed at comparable levels in myelinated and unmyelinated sensory neurons, providing a basis for the long-distance regeneration described here.     

Targeting the glial-derived neurotrophic factor and related molecules for controlling normal and pathologic pain

Introduction: Glial-derived neurotrophic factor (GDNF) and its family of ligands (GFLs) have several functions in the nervous system. As a survival factor for dopaminergic neurons, GDNF was used in clinical trials for Parkinson’s disease. GFLs and their receptors are also potential targets for new pain-controlling drugs. Although molecules with analgesic activities in rodents mostly failed to be effective in translational studies, this potential should not be underestimated.

Areas covered: The circuitry, molecular, and cellular mechanisms by which GFLs control nociception and their intervention in inflammatory and neuropathic pain are considered first. The problems related to effective GDNF delivery to the brain and the possibility to target the GFL receptor complex rather than its ligands are then discussed, also considering the use of non-peptidyl agonists.

Expert opinion: In nociceptive pathways, an ideal drug should either: i) target the release of endogenous GFLs from large dense-cored vesicles (LGVs) by acting, for example, onto the phosphatidylinositol-3-phosphate [PtdIns₍₃₎P] pool, which is sensitive to Ca²⁺ modulation, or ii) target the GFL receptor complex. Besides XIB403, a tiol molecule that enhances GFRα family receptor signaling, existing drugs such as retinoic acid and amitriptyline should be considered for effective targeting of GDNF, at least in neuropathic pain. The approach of pain modeling in experimental animals is discussed.     

Artemin has potent neurotrophic actions on injured C-fibres

In this study, we have investigated the effects of artemin (ARTN), one of the glial cell line-derived neurotrophic factor (GDNF) family of neurotrophic factors, on C-fibres following nerve injury in the adult rat. GDNF family receptor alpha (GFRalpha) 3, the ligand binding domain of the ARTN receptor, is expressed in 34% of dorsal root ganglion (DRG) cells, predominantly in the peptidergic population of C-fibres and in a proportion of the isolectin B4 (IB4)-binding population. Interestingly, only 30% of GFRalpha3-expressing DRG cells co-expressed RET (the signal transducing domain). In agreement with previous studies, treatment with ARTN prevented many of the nerve injury-induced changes in the histochemistry of both the peptidergic and the IB4-binding populations of small, but not large, diameter DRG cells. In addition, ARTN treatment maintained C-fibre conduction velocity, and C-fibre evoked substance P release within the dorsal horn following nerve injury. ARTN was also protective following capsaicin treatment, which produces selective C-fibre injury. Given the potent neurotrophic actions of ARTN on C-fibres, it may therefore provide potential for the treatment of nerve injury, particularly in the maintenance of small fibre function.     

BDNF and ARTEMIN are increased in drug-naïve non-depressed GAD patients: Preliminary data

Objective. While the role of neuronal and glial plasticity are well established in the pathophysiology of mood disorders, the pattern and measures of neuronal and glial cell line-derived neurotrophic factors are unknown in generalized anxiety disorder (GAD). The present study evaluates brain-derived neurotrophic factor (BDNF) and Artemin (ARTN) plasma levels in GAD patients. Methods. Fourteen drug-naïve GAD patients without major depression were enrolled and plasmatic levels of BDNF and ARTN mRNA were measured by RT-PCR, and compared to matched healthy controls. Results. The results showed an unexpected increase in mRNA levels of both BDNF and ARTN in patients with GAD, that appeared almost doubled when compared to healthy controls. In comparison, both BDNF and ARTN are reduced in patients with major depressive disorder. Further, the results are intriguing and might involve distinguishing pathophysiological pathways. Conclusions. This is the first report of increased levels of a neurotrophic factor and of a glial cell line-derived neurotrophic factor family member in GAD patients. While further studies to confirm these results and the functional meaning in terms of pathophysiology of GAD are needed, the potential conceptual and clinical meanings are discussed.     

Spinal cord compression injury in adult rats initiates changes in dorsal horn remodeling that may correlate with development of neuropathic pain

Spinal cord injury commonly causes chronic, neuropathic pain. The mechanisms are poorly understood but may include structural plasticity within spinal and supraspinal circuits. Our aim was to determine whether structural remodeling within the dorsal horn rostral to an incomplete injury differs from a complete spinal cord transection. Four immunohistochemical populations of primary afferent C‐fibers, and descending catecholamine and serotonergic projections, were examined in segments T9–T12 at 2 and 12 weeks after a T13 clip‐compression injury in adult male rats. Dorsal root ganglia were also examined. Two weeks after injury, fibers immunoreactive for calcitonin gene‐related peptide (CGRP) or GDNF‐family receptors (GFRα1, GFRα2, GFRα3) showed distinct injury responses within the superficial dorsal horn. CGRP fibers decreased, but GFRα1, GFRα2 and GFRα3 fibers did not change. In contrast, all groups were decreased by 12 weeks after injury. Catecholamine fibers showed a decrease at 2 weeks followed by an increase in density at 12 weeks, whereas serotonergic fibers showed a decrease (restricted to deep dorsal horn) at 12 weeks. These results show that the dorsal horn of the spinal cord undergoes substantial structural plasticity rostral to a compression injury, with the most profound effect being a prolonged and possibly permanent loss of primary afferent fibers. This loss was more extensive and more prolonged than the loss that follows spinal cord transection. Our results provide further evidence that anatomical reorganization of sensory and nociceptive dorsal horn circuits rostral to an injury could factor in the development or maintenance of spinal cord injury pain. J. Comp. Neurol. 513:668–684, 2009. © 2009 Wiley‐Liss, Inc.     

Artemin、GFRα3在胰腺癌中的表达及其与胰腺癌神经浸润转移的相关性

目的 探讨artemin、GFRα3在胰腺癌中表达的意义及其与胰腺癌神经浸润转移的相关性.方法 应用免疫组化链酶菌抗生素蛋白-过氧化物酶法和RT-PCR检测胰腺癌组织、癌旁组织和正常胰腺组织中artemin、GFRα3的表达,观察artemin、GFRα3 的阳性表达率与胰腺癌神经浸润转移之间的相关性.结果 胰腺癌组织中artemin和GFRα3阳性表达率分别为72.09%和67.44%,均显著高于癌旁组织中表达水平(18.19%,22.73%).Artemin、GFRα3在有神经浸润的胰腺癌组织中阳性表达率均明显高于无神经浸润癌组织(χ2=11.11,11.78, P<0.01),胰腺癌组织artemin mRNA 表达量(0.741±0.014)明显高于正常组织(0.101±0.031) (P<0.05),有神经浸润癌组织artemin mRNA 表达量(0.843±0.012)明显高于无神经浸润癌组织(0.512±0.017)(P<0.05).结论 Artemin、GFRα3的表达在胰腺癌神经浸润转移过程中起着重要作用,可能为反应胰腺癌生物学行为的重要指标.