University of Illinois at Chicago, Department of Neurology and Rehabilitation, 912 S Wood Street, Chicago, IL 60612, United States of America.
Wayne State University, Department of Pediatrics, Children's Hospital of Michigan, 3901 Beaubien Blvd., Detroit, MI 48201, United States of America.
Neurobiol Dis. 2020 Nov;145:105073. doi: 10.1016/j.nbd.2020.105073. Epub 2020 Sep 3.
We previously identified the Mitogen Activated Protein Kinase (MAPK) pathway as focally upregulated in brain regions with high epileptic activity and showed that inhibition of MAPK signaling reduces epileptic spiking in an animal model. Here we examined how activators and inhibitors of the MAPK pathway are expressed in human epileptic cortex and how these could contribute to the localization of epileptic signaling.
We localized gene and protein expression in human epileptic neocortical tissues based on epileptic activities from 20 patients based on long-term intracranial recordings. Follow-up mechanistic studies by depolarization of human Sh-SY5Y cell line were used to model epileptic activity in the human brain.
A clustering algorithm of differentially expressed genes identified a unique gene expression cluster distinct from other MAPK genes. Within this cluster was dual specificity phosphatase 4 (DUSP4), a potent MAPK inhibitor. In situ hybridization studies revealed focal patches of DUSP4 mRNA in layer 2/3 brain regions associated with a dramatic reduction in MAPK signaling genes. In vitro depolarization led to the rapid and transient induction of DUSP4 protein, which, in turn, reduced MAPK activity. Activity-dependent induction of DUSP4 protein was transient and required MAPK signaling. Human epileptic brain regions with lower epileptic activity had lower MAPK activity and higher DUSP4 protein levels.
DUSP4 is a highly localized, endogenous feedback inhibitor of pro-epileptogenic MAPK signaling in the human epileptic brain. Increasing DUSP4 expression could therefore be a novel therapeutic approach to prevent the development and spread of epileptic circuits.
Epilepsy is a chronic debilitating disease. Once it develops, epileptic circuits often persist throughout life. Fortunately, in focal forms of epilepsy, these circuits can remain highly localized and are amenable to surgical resections, suggesting that endogenous mechanisms restrict their spread to other brain regions. Using a high-throughput genomic analysis of human epileptic brain regions, we identified DUSP4 as an activity-dependent inhibitor of MAPK signaling expressed in focal patches surrounding human neocortical epileptic brain regions. Our results suggest that DUSP4, through local inhibition of MAPK signaling, acts as an endogenous, spatially segregated safety mechanism to prevent the spread of epileptic activity. Augmenting DUSP4 expression could be a novel disease-modifying approach to prevent or treat human epilepsy.
我们之前发现丝裂原活化蛋白激酶（MAPK）途径在具有高癫痫活性的脑区呈局灶性上调，并表明抑制 MAPK 信号转导可减少动物模型中的癫痫样放电。在这里，我们研究了 MAPK 途径的激活剂和抑制剂在人类癫痫皮质中的表达方式，以及这些途径如何有助于癫痫信号的定位。
我们根据 20 名患者的长期颅内记录，基于癫痫活动，在人类癫痫性新皮质组织中定位基因和蛋白表达。通过对人 Sh-SY5Y 细胞系去极化的后续机制研究，模拟人脑的癫痫活动。
差异表达基因的聚类算法鉴定了一个独特的基因表达簇，与其他 MAPK 基因不同。在这个簇中是双特异性磷酸酶 4（DUSP4），一种有效的 MAPK 抑制剂。原位杂交研究显示，在与 MAPK 信号基因显著减少相关的 2/3 层脑区存在 DUSP4mRNA 的局灶性斑块。体外去极化导致 DUSP4 蛋白的快速和短暂诱导，进而降低 MAPK 活性。活性依赖性诱导的 DUSP4 蛋白是短暂的，需要 MAPK 信号。具有较低癫痫活动的人类癫痫脑区具有较低的 MAPK 活性和较高的 DUSP4 蛋白水平。
DUSP4 是人类癫痫脑中促癫痫形成的 MAPK 信号的高度局灶性内源性反馈抑制剂。因此，增加 DUSP4 的表达可能是一种新的治疗方法，可防止癫痫回路的发展和传播。
癫痫是一种慢性使人衰弱的疾病。一旦发生，癫痫回路通常会持续一生。幸运的是，在局灶性癫痫中，这些回路仍然高度局限，并且可以通过手术切除，这表明内源性机制限制了它们向其他脑区的传播。使用人类癫痫脑区的高通量基因组分析，我们鉴定出 DUSP4 是一种在人类新皮质癫痫脑区周围局灶性斑块中表达的 MAPK 信号的活性依赖性抑制剂。我们的结果表明，DUSP4 通过局部抑制 MAPK 信号转导，作为一种内源性、空间分离的安全机制，防止癫痫活动的传播。增强 DUSP4 的表达可能是一种新的疾病修饰方法，可预防或治疗人类癫痫。
