Single-cell transcriptome analysis reveals dysregulation of microglial iron homeostasis in temporal lobe epilepsy

Abstract

Temporal lobe epilepsy (TLE) is the most common and drug-resistant type of epilepsy with an unknown mechanism. Abnormal accumulation of iron and lipid peroxides in the brain of TLE patients has been demonstrated. In this study, we investigated the role of microglia in iron metabolism and neuroinflammation by systematically analyzing single-cell/single-nucleus RNA sequencing data from TLE patients. Our results showed that cells associated with TLE phenotype were significantly increased in the ferroptosis gene set score and positive expression of ACSL4 and 4-HNE was observed by immunohistochemistry in brain tissues of TLE patients. Compared to the control group, microglia in the TLE group exhibited heightened metabolic activity in iron accumulation, ferritin synthesis, and oxidative damage, manifesting an inflammation-related phenotype and secreting multiple inflammatory factors. Furthermore, we discovered a unique microglial phenotype characterized by iron accumulation and neuroinflammation, resembling microglia associated with Alzheimer's disease. The abundance of these microglial cells showed significant differences between TLE patients with high and low seizure frequencies and correlated positively with seizure frequency. Gene regulatory network analysis further revealed an enrichment of inflammation and oxidative stress-related transcription factors in these cells. Additionally, we identified a TLE-related gene co-expression module whose transcriptional characterization highly correlate with these distinct microglia. Multiplex immunohistochemistry validated the expression of these cellular marker genes in brain tissues of TLE patients. In summary, these findings underscore the critical role of microglial dysregulation in iron metabolism and neuroinflammation in the pathogenesis of TLE. By identifying a specific microglial phenotype, our research suggests a potential target for developing new therapeutic strategies for TLE.

Keywords: Iron; Microglia; Neuroinflammation; Single-cell transcriptomics; Temporal lobe epilepsy.