Walls Anne B, Flynn Sean P, West Peter J, Müller Margit S, Bak Lasse K, Bulaj Grzegorz, Schousboe Arne, White H Steve
Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, Copenhagen DK-2100, Denmark.
Anticonvulsant Drug Development Program, Department of Pharmacology and Toxicology, College of Pharmacy, University of Utah, 417 Wakara Way, Suite 3211, Salt Lake City, UT 84108, USA.
Epilepsy Res. 2016 Mar;121:55-63. doi: 10.1016/j.eplepsyres.2016.01.006. Epub 2016 Jan 27.
The endogenous neuropeptide galanin is ubiquitously expressed throughout the mammalian brain. Through the galanin receptors GalR1-3, galanin has been demonstrated to modulate both glutamatergic and GABAergic neurotransmission, and this appears to be important in epilepsy and seizure activity. Accordingly, galanin analogues are likely to provide a new approach to seizure management. However, since peptides are generally poor candidates for therapeutic agents due to their poor metabolic stability and low brain bioavailability, a search for alternative strategies for the development of galanin-based anti-convulsant drugs was prompted. Based on this, a rationally designed GalR1 preferring galanin analogue, NAX-5055, was synthesized. This compound demonstrates anti-convulsant actions in several animal models of epilepsy. However, the alterations at the cellular level leading to this anti-convulsant action of NAX-5055 are not known. Here we investigate the action of NAX-5055 at the cellular level by determining its effects on excitatory and inhibitory neurotransmission, i.e. vesicular release of glutamate and GABA, respectively, in cerebellar, neocortical and hippocampal preparations. In addition, its effects on cell viability and neurotransmitter transporter capacity were examined to evaluate potential cell toxicity mediated by NAX-5055. It was found that vesicular release of glutamate was reduced concentration-dependently by NAX-5055 in the range from 0.1 to 1000 nM. Moreover, exposure to 1 μM NAX-5055 led to a reduction in the extracellular level of glutamate and an elevation of the extracellular level of GABA. Altogether these findings may at least partly explain the anti-convulsant effect of NAX-5055 observed in vivo.
内源性神经肽甘丙肽在整个哺乳动物大脑中广泛表达。通过甘丙肽受体GalR1 - 3，已证明甘丙肽可调节谷氨酸能和γ-氨基丁酸能神经传递，这在癫痫和癫痫发作活动中似乎很重要。因此，甘丙肽类似物可能为癫痫治疗提供一种新方法。然而，由于肽类通常因其代谢稳定性差和脑生物利用度低而不太适合作为治疗药物，因此促使人们寻找开发基于甘丙肽的抗惊厥药物的替代策略。基于此，合成了一种合理设计的优先作用于GalR1的甘丙肽类似物NAX - 5055。该化合物在几种癫痫动物模型中表现出抗惊厥作用。然而，导致NAX - 5055这种抗惊厥作用的细胞水平变化尚不清楚。在这里，我们通过确定其对兴奋性和抑制性神经传递的影响，即分别对小脑、新皮质和海马组织中谷氨酸和γ-氨基丁酸的囊泡释放的影响，来研究NAX - 5055在细胞水平的作用。此外，还检测了其对细胞活力和神经递质转运能力的影响，以评估NAX - 5055介导的潜在细胞毒性。结果发现，NAX - 5055在0.1至1000 nM范围内浓度依赖性地降低了谷氨酸的囊泡释放。此外，暴露于1μM NAX - 5055会导致细胞外谷氨酸水平降低和细胞外γ-氨基丁酸水平升高。这些发现总体上至少可以部分解释在体内观察到的NAX - 5055的抗惊厥作用。
