Understanding of the underlying mechanism of epilepsy is desired since some patients fail to control their seizures. The carnitine/organic cation transporter OCTN1/SLC22A4 is expressed in brain neurons and transports food-derived antioxidant ergothioneine (ERGO), l-carnitine, and spermine, all of which may be associated with epilepsy. This study aimed to clarify the possible association of this transporter with epileptic seizures. In both pentylenetetrazole (PTZ)-induced acute seizure and kindling models, ocnt1 gene knockout mice (octn1^−/−) showed lower seizure scores compared with wild-type mice. Up-regulation of the epilepsy-related genes, c-fos and Arc, and the neurotrophic factor BDNF following PTZ administration was observed in the hippocampus of wild-type, but not octn1^−/− mice. To find the OCTN1 substrate associated with the seizure, untargeted metabolomics analysis using liquid chromatography–quadrupole time-of-flight mass spectrometry was conducted on extracts from the hippocampus, frontal cortex, and plasma of both strains, leading to the identification of a plant alkaloid homostachydrine as a compound present in a lower concentration in octn1^−/− mice. OCTN1-mediated uptake of deuterium-labeled homostachydrine was confirmed in OCTN1-transfected HEK293 cells, suggesting that this compound is a substrate of OCTN1. Homostachydrine administration increased PTZ-induced acute seizure scores and the expression of Arc in the hippocampus and that of Arc, Egr1, and BDNF in the frontal cortex. Conversely, administration of the OCTN1 substrate/inhibitor ERGO inhibited PTZ-induced kindling and reduced the plasma homostachydrine concentration. Thus, these results suggest that OCTN1 is at least partially associated with PTZ-induced seizures, which is potentially deteriorated by treatment with homostachydrine, a newly identified food-derived OCTN1 substrate.

由于一些患者无法控制癫痫发作，因此需要了解癫痫的潜在机制。肉碱/有机阳离子转运蛋白 OCTN1/SLC22A4 在脑神经元中表达并转运食物来源的抗氧化剂麦角硫因 (ERGO)、左旋肉碱和精胺，所有这些都可能与癫痫有关。本研究旨在阐明这种转运蛋白与癫痫发作的可能关联。在戊四唑 (PTZ) 诱导的急性癫痫发作和点燃模型中，与野生型小鼠相比， ocnt1基因敲除小鼠 ( octn1 ^{-/- ) 的癫痫发作评分较低。}癫痫相关基因c-fos和Arc的上调，PTZ 给药后的神经营养因子 BDNF 在野生型的海马中观察到，但在octn1 ^-/-小鼠中没有观察到。为了找到与癫痫发作相关的 OCTN1 底物，使用液相色谱-四极杆飞行时间质谱法对两种菌株的海马、额叶皮层和血浆的提取物进行了非靶向代谢组学分析，从而鉴定出植物生物碱高水苏碱作为octn1中浓度较低的化合物^-/-老鼠。在 OCTN1 转染的 HEK293 细胞中证实了 OCTN1 介导的氘标记高水苏碱摄取，表明该化合物是 OCTN1 的底物。Homostachydrine 给药增加了 PTZ 诱导的急性癫痫发作评分和海马中Arc的表达以及额叶皮层中Arc、Egr1和 BDNF 的表达。相反，OCTN1 底物/抑制剂 ERGO 的施用抑制了 PTZ 诱导的点燃并降低了血浆高水苏碱浓度。因此，这些结果表明 OCTN1 至少部分与 PTZ 引起的癫痫发作有关，而这种癫痫发作可能会因使用新发现的食物衍生 OCTN1 底物高水苏碱治疗而恶化。