Neuropeptides in epilepsy

Neuropeptides play an important role in modulating seizures and epilepsy. Unlike neurotransmitters which operate on a millisecond time-scale, neuropeptides have longer half lives; this leads to modulation of neuronal and network activity over prolonged periods, so contributing to setting the seizure threshold. Most neuropeptides are stored in large dense vesicles and co-localize with inhibitory interneurons. They are released upon high frequency stimulation making them attractive targets for modulation of seizures, during which high frequency discharges occur. Numerous neuropeptides have been implicated in epilepsy; one, ACTH, is already used in clinical practice to suppress seizures. Here, we concentrate on neuropeptides that have a direct effect on seizures, and for which therapeutic interventions are being developed. We have thus reviewed the abundant reports that support a role for neuropeptide Y (NPY), galanin, ghrelin, somatostatin and dynorphin in suppressing seizures and epileptogenesis, and for tachykinins having pro-epileptic effects. Most in vitro and in vivo studies are performed in hippocampal tissue in which receptor expression is usually high, making translation to other brain areas less clear. We highlight recent therapeutic strategies to treat epilepsy with neuropeptides, which are based on viral vector technology, and outline how such interventions need to be refined in order to address human disease.     

Neuropeptides and hippocampal neurogenesis

Hippocampal neurogenesis is important for modulating the behavioural responses to stress and for certain forms of learning and memory. The mechanisms underlying the necessary coupling of neuronal activity to neural stem/progenitor cell (NSPC) function remain poorly understood. Within the dentate subgranular stem cell niche, local interneurons appear to play an important part in this excitation-neurogenesis coupling via GABAergic transmission, which promotes neuronal differentiation and integration.     

GAL/GALR2促进涎腺腺样囊性癌细胞神经侵袭的研究

目的:探究甘丙肽(Galanin,GAL)和甘丙肽2型受体(GALR2)在涎腺腺样囊性癌(SACC)神经侵袭中的作用.方法:将SACC细胞与小鼠背根神经节(DRG)共培养.qRT-PCR、Western Blot检测SACC细胞GALR2的表达;CCK-8、流式细胞术、划痕、Transwell检测GAL对SACC细胞增...     

CSF levels of a set of neurotrophic factors (brain-derived neurotrophic factor,nerve growth factor) and neuropeptides (neuropeptide Y,galanin) in epileptic children

This paper aims to investigate the possible roles of a set of neurotrophic factors (brain-derived neurotrophic factor-BDNF, nerve growth factor-NGF) and neuropeptides (neuropeptide Y-NPY, and galanin) in children with active epileptogenesis. The cerebrospinal fluid (CSF) levels of BDNF, NPY, NGF and galanin were measured with enzyme-linked immunosorbent assays in epileptic children (n = 73) and controls (n = 64). There were no significant alterations in the CSF levels of BDNF, NPY and NGF in epileptic children with active clinical seizures compared with the levels of controls. However profoundly depressed galanin levels were found in infants with epileptic encephalopathy (mean ± SD:0.63 ± 0.19 pg/ml) and significantly increased galanin levels were measured in children with drug resistant epilepsy during the period of status epilepticus (mean ± SD: 6.92 ± 1.19, pg/ml pg/ml) compared with the levels of controls. Depressed levels of galanin might reflect a defective anti-epileptogenic effect of galanin in infants with epileptic encephalopathy. On the contrary, increased CSF levels of galanin might be a result of anti-epileptogenic effects of this peptide in epileptic children with status epilepticus.     

Gene therapy in epilepsy

Results from animal models suggest gene therapy is a promising new approach for the treatment of epilepsy. Several candidate genes such as neuropeptide Y and galanin have been demonstrated in preclinical studies to have a positive effect on seizure activity. For a successful gene therapy-based treatment, efficient delivery of a transgene to target neurons is also essential. To this end, advances have been made in the areas of cell transplantation and in the development of recombinant viral vectors for gene delivery. Recombinant adeno-associated viral (rAAV) vectors in particular show promise for gene therapy of neurological disorders due to their neuronal tropism, lack of toxicity, and stable persistence in neurons, which results in robust, long-term expression of the transgene. rAAV vectors have been recently used in phase I clinical trials of Parkinson's disease with an excellent safety profile.
Prior to commencement of phase I trials for gene therapy of epilepsy, further preclinical studies are ongoing including evaluation of the therapeutic benefit in chronic models of epileptogenesis, as well as assessment of safety in toxicological studies.     

甘丙肽受体2激动剂后处理对人胃黏膜上皮细胞缺氧/复氧损伤的保护作用及其机制研究

胃缺血再灌注损伤常导致胃黏膜细胞钙超载、自由基产生过量、白细胞浸润、微循环障碍。缺氧后处理能有效减轻缺氧/复氧(H/R)造成的损伤。甘丙肽受体2(GaIR2)主要分布于消化系统和神经系统,对许多内分泌活动具有调节作用。目前关于GalR2对预防胃黏膜上皮细胞H/R损伤的作用尚未明确。目的:探讨GalR2激动剂后处理对人胃黏膜上皮细胞H/R损伤的保护作用及其机制。方法:以人胃黏膜上皮细胞GES-1制备H/R损伤模型。实验分为正常对照组(N组)、H/R组、M1145(GalR2激动剂)后处理组(M组)、SB203580(p38MAPK信号阻断剂)+M1145后处理组(S+M组)、DMSO溶剂对照组(D组)。以MTT检测细胞存活率;流式细胞术检测细胞凋亡率;Hoechst染色法观察细胞凋亡情况;ELISA法检测乳酸脱氢酶(LDH)含量;实时定量PCR检测Bcl-2、Bax、p38MAPK表达水平。结果:H/R组细胞存活率显著低于N组和M组(P0.05);H/R组细胞凋亡率显著高于N、M、S+M组(P0.05),M组凋亡率显著低于S+M组(P0.05);H/R组LDH含量显著高于M组和S+M组(P0.05);N组、M组Bcl-2表达水平显著高于H/R组、S+M组以及D组(P0.05);H/R组Bax表达水平显著高于N、M、S+M组(P0.05);H/R组、S+M组p38MAPK表达水平显著低于M组(P0.05)。结论:GalR2激动剂M1145能有效减轻H/R引起的胃黏膜GES-1细胞损伤,且可能通过p38MAPK途径发挥作用。     

高压氧对缺血再灌注损伤小鼠脑区甘丙肽含量的影响

目的观察小鼠缺血再灌注损伤后各脑区甘丙肽（Gal）含量的变化以及高压氧（HBO）治疗对其含量的影响。方法昆明小鼠24只，随机分为缺血再灌注＋高压氧（HBO）组（A组）、缺血再灌注组（B组），假手术组（C组）和正常对照组（D组），每组6只。A、B组动物采用阻断双侧颈总动脉血流30min后恢复血流的方法建立脑缺血再灌注模型。采用放射免疫分析法测定各组动物脑区Gal免疫活性物质（ir-Gal）含量的变化。结果小鼠缺血再灌注损伤后各脑区Gal含量均有不同程度的变化，皮质ir-Gal含量明显升高，海马ir-Gal含量却明显下降，与C组和D组比较差异均有统计学意义；纹状体ir-Gal含量与D组接近（P〉0．05）。HBO处理后，海马ir-Gal含量明显提高并接近正常水平，皮质与纹状体Gal含量在HBO处理后也明显高于B组和C组，差异均有统计学意义。结论Gal参与了缺血再灌注损伤的病理生理过程，不同脑区的Gal在缺血再灌注损伤中的重要性及作用可能有所不同。HBO处理后各脑区Gal含量明显提高，可能是减少缺血再灌注损伤的作用机制之一。     

Subarachnoid transplantation of immortalized galanin‐overexpressing astrocytes attenuates chronic neuropathic pain

Treatment of chronic neuropathic pain resulted from peripheral nerve injury is one of the most difficult problems in modern clinical practice. The use of cell lines as biologic “minipumps” to chronically deliver anti‐nociceptive molecules into the pain‐processing centers of spinal cord is a newly developing technique for the treatment of pain. Moreover, spinal administration of exogenous galanin (GAL) is a useful target for the treatment of chronic pain after nerve injury. Because of better histocompatibility, lower immunogenicity and reproducibility, immortalized astrocytes (IAST) have been served as a promising cellular vehicle to deliver therapeutic molecules into CNS. In this study, the rat IAST was transfected with rat preprogalanin cDNA and the galanin‐synthesizing and secreting cell line, IAST/GAL, was isolated. After cells were transplanted into the subarachnoid space of rats with chronic neuropathic pain induced by spared nerve injury (SNI) of sciatic nerve, their analgesic potential was evaluated by behavioral tests. The results showed that IAST/GAL transfected with preprogalanin gene could express and secrete significantly higher level of GAL protein in vitro and in vivo as compared with control cells. In addition, the pain‐related behaviors, thermal hyperalgesia and mechanical allodynia were significantly alleviated during the 1–7 weeks after grafts of IAST/GAL cells, which could be reversed by galanin receptor antagonist M35 temporarily. Taken together, these data suggest that subarachnoid transplant of immortalized galanin‐overexpressing astrocytes near the pain‐processing centers was able to reverse the development of chronic neuropathic pain, which offers an adjunct approach to currently used therapies for the pain management.     

Galanin microinjection into the PreBötzinger or the Bötzinger Complex terminates central inspiratory activity and reduces responses to hypoxia and hypercapnia in rat

Respiratory rhythm is generated and shaped by the synaptic interaction of neurons in the Bötzinger Complex (BötC) and PreBötzinger Complex (PreBötC) located in the ventral respiratory column of the medulla. Metabotropic receptors are important modulators of fast neurotransmission in the generation and shaping of respiratory rhythm. Microinjection of the neuropeptide galanin (1 mM, 50 nL, 50 pmol) into functionally identified BötC or PreBötC in urethane anesthetized, mechanically ventilated and vagotomized rats caused severe dysrhythmia or persistent apnea. In the BötC and PreBötC, galanin reduced the ventilatory response to hypercapnia (5% CO₂) by 21% (P < 0.001) and 38% (P < 0.01) respectively. In the BötC and PreBötC, galanin reduced the ventilatory response to hypoxia (10% O₂) by 15% (P < 0.05) and 23% (P < 0.01) respectively. These results indicate that microinjection of galanin into the BötC or PreBötC depresses a neural substrate required for the generation of respiratory motor output and reflex responses to hypercapnea and hypoxia.     

Inter- and intra-nuclear differences in galanin expression between the hypothalamic paraventricular and supraoptic nuclei in colchicine-untreated rats

Not much is known of the topography of galanin expression in the hypothalamic supraoptic (SON) and paraventricular (PVN) nuclei neurons in colchicine (an axoplasmic inhibitor)-untreated animals. Insight into the biological implication(s) of galanin expression in the PVN and SON will depend, at least in part, on the nature of its distribution in colchicine-untreated animals. In this study therefore, the topographical distribution of galaninergic profiles was examined in the PVN and SON of colchicine-untreated rats. Staining in the parvocellular PVN (PVN(p)) was predominantly as varicose thin galanin fiber processes while the magnocellular PVN (PVN(m)) contained large cell soma and fiber processes. The relative fiber density was higher in the anterior, periventricular and medial PVN(p) than in the dorsal, lateral and posterior subdivisions. Large-sized cells and thick fibers were limited to the posterior PVN(m) while the anterior and medial PVN(m) contained varicose profiles. Light- and intensely-stained galanin-positive cells as well as large- and small-diameter (varicose or non-varicose) fibers were observed in the SON. The large and thin fibers exhibit preferential ventral and dorsal distribution, respectively. Together with the complexity of specific afferent and efferent connections within the PVN and SON, these observations underscore heterogeneous galanin expression and raise potential implications for understanding the biological role of galanin by physiologically challenging stimuli.