CircSpna2 attenuates cuproptosis by mediating ubiquitin ligase Keap1 to regulate the Nrf2‐Atp7b signalling axis in depression after traumatic brain injury in a mouse model

Abstract Background Depression is a common but often overlooked consequence in individuals with post‐traumatic brain injury (TBI). Circular RNAs (circRNAs) play essential roles in the nervous system, yet their involvement in the cell death mechanism known as cuproptosis and in TBI‐related depression remains unclear. Objectives This study aimed to investigate the role of circRNA, specifically circSpna2, in the regulation of cuproptosis and its association with depression in TBI patients. Methods RNA sequencing (RNA‐Seq) was used to assess the differential expression of circRNAs. Depression was evaluated using subjective and objective rating scales, and circSpna2 expression levels in plasma were measured. Further functional experiments were conducted in TBI mouse models, including knockdown and overexpression of circSpna2, to explore its impact on the Keap1‐Nrf2‐Atp7b pathway and cuproptosis. Results TBI patients exhibited decreased levels of circSpna2, which correlated with depression (p