Expression of the Interleukin 6 System in Cortical Lesions From Patients With Tuberous Sclerosis Complex and Focal Cortical Dysplasia Type IIb

Abstract

Tuberous sclerosis complex (TSC) and focal cortical dysplasia type IIb (FCDIIb) are characterized by epilepsy-associated cerebral cortical malformations. To understand the potential role of the inflammatory cytokine interleukin 6 (IL-6) in the pathogenesis of these lesions, we analyzed the IL-6 system in TSC and FCDIIb cortical lesions and in control cortex (CTX). Greater messenger RNA and protein levels of IL-6 and of its receptors (i.e. IL-6 receptor [IL-6R] and glycoprotein 130 [gp130]) were observed in TSC and FCDIIb lesions versus CTX. Immunohistochemical analyses indicated that IL-6 and IL-6R were strongly expressed in misshapen cells, namely, dysmorphic neurons, giant neurons, and balloon cells. Glycoprotein 130 was diffusely expressed in nearly all cell types. Most IL-6/IL-6R+ misshapen cells colabeled with neuronal rather than astrocytic markers, suggesting a neuronal lineage; most IL-6/IL-6R+ balloon cells in FCDIIb expressed glial fibrillary acidic protein. Protein levels of Janus kinase 2 and phosphorylated signal transducer and activator of transcription 3 were greater than in CTX, suggesting involvement of the gp130-Janus kinase 2-signal transducer and activator of transcription 3 pathway in IL-6 signal transduction. Soluble IL-6R, but not soluble gp130, was greater in TSC and FCDIIb lesions than in CTX, indicating activation of this trans-signaling pathway. These results suggest that overexpression in the IL-6 system and activation of IL-6 signal transduction pathways may contribute to the pathogenesis of cortical lesions in TSC and FCDIIb.